Your choices are fine. So long as you like playing as those professions, that's all that matters - not whether it makes you that guy or not. That said, and I'm biased here, but I think people don't give the Mesmer nearly enough credit. It has a ton of utility in virtually every part of the game and really shines, IMO, in WvW. For overall usefulness, I would put Mesmer above Ranger for WvW.
Warriors will get a slight nerf, but other than that it's a very solid, fun profession to play. [i am guessing about the nerf, but it seems unavoidable]
Of your four choices, Thief is the one I think needs the most help; it's simply not the best at anything.