No they really don't. People have tested this. The only class they matter for more than a percent or two is monk. That is not annihilating your dps. Why? Because even ignoring positionals you will still hit some. People struggle enough already with the much more complex rotations of the melee dps, no need to go on to pile on you must go for positionals on them. Hell even the Ultimate clears I've been watching, the the melee largely ignore positionals.