I completely agree with the stance on Alec's lines, and I think he's one of only two characters on the show who's stuff is perfect and always funny, the other being Kenneth. The only thing I want from him is more jokes, more jabs, last season everything out of his mouth was either a deliberate or inadvertant insult to Liz, whereas he seems a lot more laid back and apathetic this season. This is the kind of thing I'm talking about when I say they aren't trying hard enough in places.
The main problem I have when it comes to timing and delivery is Tracy. I think he's incredibly forced most of the time, and the timing and pacing on his lines never does it for me. Take the newest episode, where he said "would you ask a tiger not to turn back into a Chinese person at midnight?". That was a really funny line, but the way they did it really held it back. They were walking, and then he stopped and turned around to say it, and said it very directly, and I dunno, I just think it should've been far more off-handed and aptly paced, and the way they did it killed the momentum behind the line. Momentum is crucial to a show like this, the same way it was with Seinfeld and AD. Jokes have to be delivered like a juggling act with an ever-active system of punchlines bouncing off each other in perfect rhythm.
About 10 or 15% of the time, peaking around the middle of last season, the show has a great handle on that, but most of the time it just never quite cuts it for me nor gives me cause to believe that in the scenes where the show succeeds it does so because they know what they're doing, rather than out of chance.
Combine that with the seemingly increasing amount of time wasted by the really dumb humour and characters, like Tracy and Jenna, and it's really starting to lose my interest.