One thing is a spec being less strong by design. Another thing is said spec being designed around a specific item, which person may or may not have. Thats my issue with the legion legendary system. I personally had experience with what I am talking about. I raided in EN as guardian/feral as with my guild we used 3 tanks on 3 EN fights. For the rest, tanks rotated, so when I dont tank I either had to DPS or be benched. My feral OS simmed about 180k with crap leggos and around 875 ilvl. The moment I got the 2nd BiS item(the shoes that give stacks of Predatory Swiftness) the dps went above 310k. Same gear, same rotation. Now, on a fight with ~320k dps check you will not bring a person with 180k, but you can afford to do that if they do 310k(as few classes already did more than the minimum). Which is why I only did Ursoc as feral when I got that legendary. Before that I either tank it, or sit out. And I personally knew few people playing feral ONLY. I get if such person is benched because feral is bad for X or Y boss. But being benched because you dont have specific item is just retarded
Wanna know how top guilds "avoided" benching ppl due to leggos? By not having those specs in the first place. Example: Nagura, THE boomkin in the EU raiding scene was given the choice to either heal those bosses, or sit out, UNTIL she got the boomkin legendary helm which helped TONS on ST fights