Right-o. Most Mega-Evolutions tend to stick to hyper-offense or tanking (and whatever it is that Abomasnow is supposed to be doing). Shame... I was hoping for Mega-Miltank, with like Lugia bulk...
However, 56k had a point. Although yes, Choice Trickers generally target Walls, there's still a definite drawback in that (a) the opponent can potentially switch in on the Choice Tricker and set up, and (b) (a bit more indirectly) people may potentially (can't stress that enough) be less likely to run Walls and instead opt for the bulky tanks/nukes that are the Megas, thus cutting down on the niche that Choice Trickers hold.