You fail to realize that loosing threat on a hunt zerg does not actually affect you in any tangible way besides "Darn it! I want to make more enmity!". You dont loose points. You dont loose anything. Heck, we dont even hunt the way they were intended to be hunted. Basing balance around an activity with no winners or loosers at the expense of other content which does is a poor method. No one is 'excluding' Drk from their hunt parties because of the War meta. If a job is notably underpowered in content with strict win conditions, those players are now going to suffer stigmatism from the community.
Hunts dont have any weight in the world. I never said raids are all that matters. There is lots of content that matters when it comes to tank performance. Nearly everything in the game is relevant when it comes to balance. I remember being excluded from dungeons in 2.0 on war in favor of plds as war couldnt mass pull. I remember plds being excluded later because flash did no damage in dungeons. Dungeons matter. Raids matter. 24 mans matter. Extremes matter. PVP (in its own separate world with its own balance and actions) matters. Leveling experience and balance pre 70 matters. Hunts, dont matter (for balance).
Hunts are literally the lowest priority of content to worry about balance on. That is not to say that hunts arent useful/fun/valuable content or that players that hunt dont matter. But job balance in hunts doesnt. There is no notable loss/punishment/exclusion/stigma/negative side effects of job imbalance in hunts. There are consequences to poor balance in virtually any other aspect of the game. All tanks are capable of adequately tanking any hunt defensively and can generate more enmity than any non-tank, and have enough enmity to cap points in large groups exceedingly effectivly. The fact that X tank can do it 1 gcd faster is utterly irrelevant.