They were basically just trying to do what they did in Season 2, since they had a battle coming up. The entire season of the Night's Watch arc has been one long delaying tactic so they could put the battle for the Wall in a big single-location penultimate episode and recapture what was in some ways the previous high point (other events got talked about more, but that was due to the extreme tragedy and/or shock value) of the show.
And they even added a bunch of stuff that was not in the books to try and hit those same notes, like the ranking leader, already despised for his part in Ned's murder, letting someone else command the battle and eventually sneaking to preserve his own hide, or the boy saving the main character with a last minute attack from behind.
I wonder if next season, Jon & Edd will be eagerly pressing Ollie for the tale of his exploits in Mole's Town after they send him to the brothel out of gratitude?
It wasn't a bad episode, and the action was probably the best they've done on the show so far, especially on a large scale (it was pretty obvious that there were not large armies behind the handful of guys you actually saw fighting in Blackwater), but dramatically, the characters even admitted at the end that nothing had changed as a result of their efforts, whereas Blackwater was a complete reversal of fortunes that set up the status quo for the next season. This? Not so much. In the book, having at least three different battle scenes at the wall, with the increasing attrition of each one wearing down Jon & the brothers, you could see where he would make the decision he makes at the end of this one. Ironically too, I think the circumstances under which Jon heads out for his suicidal assassination attempt in the book might have better fit with the situation on the show. As a result of the great big battle, with Jon leading, slaying the Magnar and capturing Tormund, he'd be a major obstacle Slynt would want out of the way, giving him an additional political motivation to send Jon to his death.
But, rather than spend all those extraneous episodes with Gilly or the brothers talking a bunch, or a made-up raid on Crasters, or Ygritte being a bitch while she and her companions wandered the Gift, if they had just had the series of smaller battles, maybe the hopelessness of the situation, and paucity of their resources would have been better conveyed. There was really no justification for doing it this way, unless the showrunners felt some sort of compelling need to recreate the previous high water mark for epic battles on the show.
Another reason they did it this way are directorial and budget motives.
They could get a lot more worth for their money by letting a single director handle this during a single episode than they would have gotten by giving it to three directors over 3 episodes. A whole lot of money would have been wasted had they done that, and we would have gotten smaller battles. A single guy, focused on filling 50 min, could do much more with what he had, and provide more character moments and build up to it as well. That also let them show this as one big battle set at night (again), which greatly reduced the effect costs.
But as for trying to top Blackwater from s2, you're of course right it was their goal. In scale and now much they managed to show on a (massive) TV budget, they did it, but dramatically.. I agree with you they did not top it. There's something about it that's sort of futile too: the audience is used to seeing that stuff in movies, even with the money they put into that episode, it's really hard to truly wow an audience with just that kind of stuff.
I actually didn't like it nearly as much as I did Blackwater, where Lena Hedley pretty much stole the show with her gloomy and bitter drunken Cirsei scenes, the Hound-Sansa one etc. The character stuff was just much better handled in the Blackwater episode, and the impact/twist of the Lannister victory was just much bigger too.
Yesterday's show lacked that dimension, but aside from the writing (which wasn't bad, but not stellar) it's mostly due to their much lesser success at making the audience care for the NW characters and the wildlings than they do for Arya or the KL stuff. That owes a bit to the lack of depth in their development of that story arc so far, centering it a lot on the "young ones" vs. Thorne, not having many other identifiable players involved (which now they got rid of the "buddies" and soon of Sam, might change).
A great deal of the non-readers also perceive that story line as a minor one, a sideshow to the "game of thrones" in KL and Meereen. A lot of the "action movies" fans loved the episode for the adrenaline rush and its scale for a TV show, but there seems to be a lot of people who were disappointed that it was a full Wall episode when after last week's it's really the follow up to KL stuff they're eager to see.
Someone suggested that perhaps they should have switched the order or that one and episode 8, but I don't think this would have been better. I'm not sure that having three 15 min. battles over three episodes would have been better either.
I tend to agree that having Janos order Jon to go kill Mance would have made sense, but it looks like they decided to make it Jon's decision so afterward and because he makes a deal to let the Wildlings come south he will be accused by Slynt and Thorne to have betrayed the NW, while at the same time Janos now has something over Sam because of Gilly while Sam can undo Janos because Gilly can testify as to his cowardice.
I'm not sure where they're heading with that. If they want to rush through Jon's election, they can probably do it this way:
Janos (and Thorne? I presume Thorne might be in bed a while.. maybe Janos will take advantage of it to put himself ahead of Thorne?) will move while Jon is away, and call him a traitor/deserter who has gone to Mance and of course it would set him up for execution if he's caught. Janos might try to silence Sam using what he saw of him and Gilly, but Sam will have to take the risk to expose it himself by spreading the story of Janos's cowardice, so that when Jon arrives with Stannis and the wildlings, he isn't executed but welcomed as the new Lord Commander.
This can probably be done with a few Castle Black scenes only, but they have only 66 min. left overall, including action scenes/battle with Mance, a Mance-Jon face-off, and some Stannis-Melisandre meeting with Jon-Mance beside, so want it or not it would be really rushed to make Jon LC this year... not to mention the sheer lack of logic that the NW would hold their election NOW.
The other thing they may do, though, is the opposite: not return to CB this year at all, keep all this for Jon's reintroduction in s5, in which case ep. 10 will end with him agreeing to let the Wildlings come south, and Stannis offering to Jon to legitimize him and give him the North, which would also make a good cliffhanger. When Jon re enters CB in s5x01 he gets accused of treason by Janos, who fears the influence Jon gained from his role in the battle and what will happen to him if Sam talks. As for Thorne.. we'll see where he stands.
I guess I find option 2 perhaps more likely given the set up they put in place, as it would also let them introduce a few new figures at CB first, from the Eastwatch and Shadow Tower people coming for the election.
Some think they've mentioned too much election stuff already not to have it in ep. 10, but they did exactly the same with Joffrey's wedding last season.. build it up in advance so they could deal with it early in s4, not to wrap it in s3.