Slippery slopes, my friend. It was that mindset (weapons to rule them all) which gave rise to the lameness of the top-tier infiltrators that break everything with no teamwork whatsoever. I just oppose it out of principle. 
Well, I don't think so, actually. Stupidly OP infiltrators have been around from the start, and were created by Bioware when noone even knew that cooldown would depend on your loadout. Hell, they even got nerfed and they're still awfully broken!
The trend you can see, with kits and powers getting more and more powerful one DLC after the other, is a trend which is actually common to many multiplayer games and it's called power creep. Don't think it's necessary to delve too much into a discussion about it, but the important point is that, in my opinion, it has nothing to do with people enjoying a different playstyle on some kits than others do.
The thing you can notice, with the evolution of kits in this game, is that they became easier and easier to play. Again, part of that is usual power creep I guess, part is probably Bioware going in that direction because of reasons apparent to them, and only them. On the other hand, using a heavy gun like a claymore on a class like a FQE does *not* make that class easier to play. At all. Actually, it makes it harder to play at first, and you definitely need your share of learning about how to behave with her. Then once you do, the skill ceiling is higher, and the result is that a claymore FQE is, I believe, much more efficient at killing than most of the light (and not) guns.
So you see, I do not see this connection between people enjoying heavy guns on some kits and Bioware deciding that the best way forward for the multiplayer consisted of introducing brokenly easy to play kits. I just don't see it. I see Bioware giving us an extreme amount of freedom in deciding which character to play, and how to play it, and I see people obviously making different choices, because the world's nice cause it's varied. And I don't see anything wrong in that.