I feel like the innate DPS isn't the problem, it's that it's so easy to screw them over, because they need 20 seconds of uninterrupted uptime, and Inner Release coming off cooldown tends to occur during times where mechanics are going to screw them over.

O2S is an excellent example of this: if you use your immediate IR combo, then it comes back up roughly at the time the boss uses Long Drop, which will absolutely wipe the group if you don't click it off.

Besides, the only utility they had for the game until SB was the Storm's Path debuff, but it got removed to try and balance tank needs (and was replaced by more DPS by increasing gauge built). No tank can get DPS utility, because it's way too high in demand. If one gets it, then they all have to get it, but then it balances out to zero difference, so it's pointless to add.