I agree that trying to mimic RJ would have been a mistake, but as you say, the vocabulary could have been better matched. I am kind of ambiguous about the Mat humor in tGS, and I suppose that is another case of it being just as well that B-Sand went his own way rather than try to handle it in RJ's style. However, as you point out, other characters are funny, too. He seems to have labeled Mat as the Comic Relief, and made a conscious effort to write humor into his storyline, and completely neglect the potential humor elsewhere. For example, some of the funniest things have come out of Nynaeve's mouth, albeit unconsciously, but then Mat was not really one for wisecracking either. The humor in his PoV, IMO, came more from his askance perspective on things other characters took seriously than his dialogue. Thom was better at the ironic asides in RJ's books too. He is more of a straight man with B-Sand.

As you say about Elayne, there was a lot of humor in her PoV too. She was kind of a very subtle Margaret Dumont for WoT as the one who keeps encountering myriad inconveniences. Getting hit by problems, instead of pies, as it were. I guess we'll see how that goes.