Because they are, as you say, sackless idiots. They don't go stomping around as majestic avatars of destruction and terror, because that's a good way to get whacked. They prefer the safety of a hidden refuge, of maneuvering in the shadows, and of ruling behind the walls of a fortress with an army on command. Given the choice, most of them would not show up for Tarmon Gaidon, because they don't care about how badass that would be. The viking mythology is among the most badass, and they're all eager to show at Ragnarok, despite certain knowledge of defeat, while the Forsaken would forsake even a ringside seat to their victory, out of fear of getting killed. There is badass, and there is evil, and the Forsaken are definitively in the latter category and well away from any Venn-diagram intersection of the two.

That's not so much an argument as a protest regarding what kind of scene you would prefer.

Why? She was pissed at her boyfriend and jealous at the slut who let him cheat. This was in no way, shape or form the culmination of some master assassination plot or long-range strategy. She got wind that Rand was up to something, showed up to investigate, heard he was sleeping with someone else, and lost her shit. I don't know how that is implausible in the least.

And sometimes it just makes sense and is the actual reason. Your scenario is borne of nothing more than a sense of drama and what would have made the most "awesome" scene in your mind, regardless of adherence to any narrative causality.

Lanfear didn't care about Lan, except as an object that presumed to threaten her, so she swatted it away like a fly. The Warder bond gives more than enough explanation for why he would survive a simple weave of air to knock him flying.

You are not supposed to fear them any more than the Trollocs. From day one, the emphasis has always been about the Dark One. In hindsight we see that Ishamael wreaked havoc and terrorized the ta'veren, but that is only in hindsight. At the time, he was scary because we thought he was the Dark One. The enemy from the very beginning of the series has always been presented as the nigh-omnipotent epitome of evil and chaos, and his presence has always been the source of the real worrisome threats, such as the unending winter and summer at various points in the series, the bubbles of evil and now the corruption of nature, the perversions of space and time, and the random and unavoidable deaths. The petty evil wizards who kiss his ass and grovel to him were just another example of his evil and the threat he posed, that he could allow the very worst impulses of humanity to find their level and outlet in his service. Most of their legends serve to counter-indicate the threat they pose. Semirhage is scary because of the ways of dishing out pain that are available to her beyond the normal limits of flesh, but she is not a serious threat because sadists are not really dangerous. They are too involved in their own appetites and fetishes, and like an addict, will forgo the smart move in order to prolong their enjoyment. People ALWAYS ridicule and criticize the arch villains and evil overlords who sentence the hero to a slow and exotic death, rather than whacking them as soon as possible, or stopping to gloat over their ultimate scheme and reveal the details to the hero, but all they are doing is indulging the same impulse that characterizes Semirhage - sadism and ego! They want to watch the hero die dramatically, or they want someone to acknowledge the evil or the extremity of their magnificent scheme (their minions are unable to properly appreciate the schemes, because they have been hard at work carrying them out, and from their point of view, it's just the job at this point). In all cases, the hero survives and escapes because the villain had a motivation to keep them alive. Semirhage is nothing more than a Bond villain in disguise. Even her greatest act of destruction, wiping out the Seanchan rulers and plunging the Empire into chaos will undoubtedly serve the Dragon Reborn in the end. She put his best friend's wife in charge, after all, and not only that, placed the rump Empire in the wetlands in a much weaker negotiating position. If Tuon was reporting to her mother back home, she could never have agreed to any sort of equal alliance with the Dragon Reborn, but would have had to insist upon supremacy, and Radhanan, by the brief descriptions we get would have been much less amenable to cooperation. Instead, thanks to that single thoughtless act of destruction, we now have a much better chance for the restoration unity and order that the books imply is so necessary for Rand to win. There is no reason, aside from their superior educations, to assume anything great or intimidating about the Forsaken. The threat has always been the Dark One and one of his worst attributes is how he brings out the worst in people, of which the Forsaken are walking illustrations.
If they were competent, credence could be given to their own contention that they are simply fighting to allow the most worthy to rule, yet by their own incompetence, we are shown that the Shadow lacks even that virtue, instead allowing incompetents to rise to great power and rulership, and permitting them to stay there, because of the evil deity backing them up. Recall that after three years of winning the war, with the Dark One behind them and growing in power as time passed, and increasingly freeing himself and turning people to his side, LTT knocked them back on their heels and was WINNING the middle part of the war. Eventually, the Dark One's power was too great and forced the Strike at Shayol Ghul, but remember that these nimrods almost lost despite their numerous advantages.

Yes, being visible in the sky to everyone for miles around is a PERFECTLY NATURAL AND NORMAL THING.
I am not scrounging for an explanation, I am simply offering one of the many possible explanations of the patently and glaringly obviously preternatural circumstances of their encounter. And of course they were there in the flesh - we certainly never saw Rand going to sleep. But Rahvin was in TAR in the flesh when he fought Rand, and how much good did Nynaeve's channeling do against him? Why was Moghedian so terrified of encountering him or Rand? Why, for his killing blow, did Rahvin turn TAR against Rand, rather than use weaves? Plainly the former works better in dream-related stuff than the latter.
In any event, it is obvious that there was SOMETHING supernatural at work and maybe it had to do with the Horn of Valere, but by all appearances, it was Ba'alzamon who initiated the confrontation and thus probably responsible for the circumstances. In such a case, perhaps it was taking all his strength to maintain the theater of conflict.

Mere unsupported opinion.
Who is to say he was even capable of channeling, or that his weaves would be able to directly affect Rand? If he was still partially bound, or in some way linked to the Dark One, the distance from Shayol Ghul might have been too great, particularly if he was far gone enough to be exclusively using the True Power, as Moridin later does (the fire-eyes have been reasonably postulated as an advanced stage of the saa). There are all sorts of reasons why channeling might not have worked for him. For one, Rand was linked to the Heroes of the Horn, and channeling had no effect on them either, and Mat, Perrin & Hurin all returned from a battle against damane rather unscathed. Since we have NEVER seen another character channel in identical circumstances, there is no reason to believe that he could.

Because willpower and belief are stronger than any awareness of technique in T'A'R. All Nynaeve needed to beat Moghedian was the certain knowledge that she had an a'dam about the Forsaken's neck, and all the rest of Moghedian's technique was as dust. Also, I doubt that it was entirely in TAR since even the HotH believe nothing in T'A'R affects the real world. I think they might have been in some halfway state that was projected so strongly into the minds of the surrounding people that they thought they witnessed the battle with their eyes. All sorts of other explanations abound, including a side effect of the Horn, which could also explain the extraordinary abilities displayed by the HotH, including immunity from the Power and riding a horse over water and ship-killing arrows. There was a whole lot of freaky shit going on and too much to assume you know what either party in that fight was capable of.

In WoT, a liberal application of T'A'R can do that. And your reasoning is unsatisfactory, since all you are doing is refusing to play the game. EVERYTHING is because RJ wanted it that way. He is the very talented writer whose books inspired a large online community. By your own argument, you're just a guy who has a different opinion of what he should have written, and given the success of his version, the evidence would seem to support that vision.

So what? This is not some sort of Magic:The Gathering game, where the high card decrees victory in a confrontation. WoT has made it clear that channeling is no more than another weapon. Yes, the guy who brings a knife to a gunfight will probably lose, but that does not mean a guy with a knife can't beat a guy with a gun. The Aes Sedai are, generally speaking, the only channelers in the world (and more importantly, consider themselves the only channelers, and the best channelers), and perfectly able to use the Power in self-defense, as well as in numerous non-weapon capacities, and yet they still bond warders.

And you have no evidence for that other than your random opinion. Even if he WAS there in the flesh, there is no proof that his channeling would have worked, or that he was capable of anything other than the True Power, or that the TP would have worked so far from Shayol Ghul with at least four Seals still active, or that it would have worked against the Horn of Valere. Since, as I noted above, the Heroes are protected from the Power, maybe the Sounder of the Horn is protected as well while they are there, which would explain why he did not even bother trying.

Who cares?

And those are almost always evil people acting out of good motives or a perverted love for something, like Ingtar, or Couladin, or Byar, or Egwene, or Dark Rand, or the 911 terrorists, or Hitler. People with guts or spines or self-respect are as unlikely to have been as skilled at kissing the Dark One's ass. With courage and valor and determination, particularly if the AoL was the meritocracy it is often perceived as, they would have been able to find success in other ways, and not needed to cultivate the skills of a courtier and sycophant and thus fallen to the treacheries of their contemptible colleagues in the Shadow.

Really? Because most readers, and critics, seem to find complex and multi-dimensional people make better villains. The Wheel of Time series is about overcoming your OWN flaws. It is about an evil that cuts the ground out from under you, while tempting you with power and license. The greatest human threat explicitly since the middle of the series, and even hinted at from the very beginning, has been of good guys going rotten. Aridhol was introduced as a cautionary tale in the very beginning of the series, along with Padan Fain! The greatest menace extant in the world at the start of the series was tainted-saidin, not because it killed the users, but because of the evil deeds it drove them to perform. When Rand learns he can channel his greatest fear is not his own death, which he had already faced, but that he might harm those he loves. The very first thing we see in the series is a man walking through a charnal house of his own making and it is soon made clear that this is a good guy, a hero and savior figure, who has wrought this devastation. WoT is not about external threats, it is about the threat within. The climax of Perrin's private arc is not defeating the Shaido and reclaiming his wife, or beating Galad in a trial or defeating Slayer and inadvertantly helping Rand and Egwene, it is about overcoming his own weaknesses and hesitancy and stepping up to assume the mantle of leadership and responsibility and agreeing to undertake the task necessary. Mat's story is not about his heroic deeds and asses kicked saving Tuon and Moiraine, but of the sacrifice he made for the latter and more importantly, his acceptance of his role as a leader and his ultimate acceptance of the implications of the Aelfinn's prophecy. He first had to accept Tuon as his wife and that enabled him to make the deliberate and conscious offer of half the light of the world. And finally, there is Rand. Anyone who doubts that the ultimate climax of his story was his moment of reflection on the peak of Dragonmount has far too inadequate a grasp of the story to bother talking to.

The villains to be overcome in WoT are the characters own flaws and weaknesses. Rand himself, in his apotheosis as the ultimate combination of Dragon and Dragon Reborn, states the reason why he can succeed where LTT failed was that he was brought up better this time. Does this mean that archery or your hypothetical sheep-shearing contest will be the key to Tarmon Gaidon, or could it be because the fight is, and always was, about character, and Rand has that quality to a degree LTT never did?

When the series is viewed in this light, the Forsaken are perfect antagonists. The point is not "Look at how badass Rand is for killing those mighty Dark Lords of power and destruction." The point is "This could be Rand if he fails or falls." The point is, "This is who gets the world if Rand fails or falls." WoT is not about overcoming the Forsaken, it is about overcoming your own worst tendencies and an ultimate villain who would as soon corrupt you and destroy your being and your self and soul as he would your physical body.