But that sort of mission, Isam would far more likely get from Moridin.

You're close about the options with Rand, but it's more deductions we made over the years than any strong statement in the series.

The "have Rand do more damages to his side" angle is from "Let the Lord of Chaos rule" theme, and the best background info we have to tie to Rand is from the "Big White Book", where we found out the Lord of Chaos/Misrule is a name from a WOT Feastday (inspired by the Lupercaliae, medieval carnival and the whole Inverted World motif) elsewhere he's called the King of Fools. It's about raising the village fool as King for a day, and letting him preside over chaotic celebrations. It's pretty obvious looking at concrete medieval examples of "inversions" that this was a major source of inspiration for Jordan.. Queens are turned into servants, an village innskeeper daughter is raised "Abbess", a farmer's son is married to an Empress who's turned for a while into a thieving servant etc. Anyway, knowing the source of inspiration for all this... it's fairly obvious the Lord of Chaos Rule saying used by the Shadow refers to that King of Fools doing more damages to his own side than good. But it wasn't stated in clear by anyone so far in the books.

The other two have been referred to but not exactly explained by Ishamael/Moridin. We still don't know for sure why Moridin and the DO want Rand alive, to die in specific circumstances. It's clear the Shadow would have preferred to turn Rand to their side. Having him die in specific circumstances and (as Ishamael once said) "serve in death" seems to have been once the plan B.

I agree with you that Jordan didn't do all that well with his villains. He didn't find a good balance between stretching suspense over such a long series and developping his villains in interesting ways. Oh for sure that kept us theorizing all these years amd he wanted to give us the feeling the world was vast and no one understands nearly all of what's going on, but the closer we get to the ending, the more obvious it is that what RJ developped and had happened behind the scene with the Forsaken is a lot more interesting than the hard to puzzle out tidbits shown on-screen. He seriously underused his villains through most of the series, kept their motivations way too hidden. Perhaps there are many revelations about what went on earlier coming that will make the early books more interesting (and perhaps more clever than they appear now), but I'm sceptical.

And mind you, making each one an icon of an aspect of human nature Jordan loathed wasn't exactly the way to end up with very complex characters, especially not psychologically. I still kind of like Moridin and Lanfear, and Graendal when written by Jordan (ie: when she still had a superior IQ). Demandred for me is a wait and see case. I never found him all that interesting because he never had much to do, and like most of the others he's so basic: talented man in the shadow of a more talented and luckier man ruins his life by being consummed by envy. Yawn. His military genius might be interesting to see in play, but I get the fairly bad feeling that's an aspect where we'll miss the Jordan-the-military-history-buff badly (ie, whatever Jordan set up for Demandred, I doubt Sanderson even with the help of Jordan's assistant who's a military buff was be able to write a military genius all that well) - and I suspect we'll see Demandred at work mostly from the POV of his foes, without great insight into his plans from Demandred's POV. And that's too bad.

The only thing I'm highly confident about is that the pieces of the puzzle will all fit into place nicely. Jordan conceived the Last Battle before he started the series and developped the major points going from there and back to the begin backward. We've paid the price of that method often enough (as it's no doubt responsible for much of "I need to stretch X here a bit because Y isn't ready, and my hands are tied about what X and Y will do next together", but at least with TGS/TOM we started getting the pay-off, which is that a very great deal of details we thought was more or less "fillers" turn out to quite relevant in the endgame (sending Shemerin in hiding in TV by book 5 so she'd be there to lead Siuan into the city in the finale.. now that's planning), and unlike so many finales that ended up as train wrecks due to bad planning or too much making-it-all-up-as-I-go-along writing, WOT's seems more "in control" (too much maybe, I fear a little the "not enough was irrelevant and everything fits too neatly" problem). Whatever the execution as novels, and God knows they're flawed, Jordan was certainly clever.