Tbh, I hate arguements like this, because it discredits any arguement around balance and simply says "If you don't like it/think its broken, dont play it". In fact, the question shouldn't be "Why not ignore OP class?" and instead be "Why should I play any other class?". If the game provides little to no incentive to play the underpowered class, then the balance should be a concern.
I dunno, it does sound like it's being seen almost as an exploit so I can see the reason for the comparison. From my perspective I guess the incentive is to not do something you don't enjoy: I suppose I would view playing as a class you feel to be overpowered as much the same as playing on the easiest difficulty and then complaining that it's not hard enough. Then again, I have actually seen someone saying exactly that.
As I've said elsewhere, I'm not actually a very skilled tactician or combatant but I'd rather lower the difficulty or deal with it than adopt a style of gameplay that doesn't agree with me. I suppose in that latter regard I'm surprised anyone would do otherwise.
