Honestly from doing a bunch of endgame dungeons, I feel like (in comparable gear) every dps class is pretty dang close to every other dps class. Nailing your rotation and playing your class well are going to be much bigger factors than which class you happen to be, that's how tight everything seems to be. Sure some fights will favor certain classes over others, but a skilled player will make up that difference every time.

Basically, give me a talented player playing a "lesser" class any day over a "best" class played by a mediocre player. You do zero dps when you're dead.