You are balancing for a theoretical fight. Every fight can be done with 0 tank stance outside of the pull. And the pull isn't for mitigation.
Warrior doesn't have access to inner beast, and it doesn't need it because content isn't designed to need frequent access to an on demand cooldown, and thats because warrior doesn't have frequent access to on demand mitigation.
So once again, content is built around tank cooldown kits, which means warrior must be kept in mind, which means frequent mitigation isn't required. But then this is used as a balance point for warrior having boosted dps and more flexibility with less costs. This isn't an actual draw back. An actual drawback is dark knight needing to spend dark arts on dark mind because it does run out of cooldowns in some fights and TBN or dark mind on their own aren't enough or need to be used close together. Thats a drawback, you have to give up dps for mitigation in boosting dark mind, and its one which actually currently exists.
We have had this conversation before. Maybe if you try solo-tanking you might have an issue, and even there I'm only giving a maybe. If you co-tank and split the fight appropriately then warrior does just fine if not better, and doesn't require any of the other tanks utilities. There isn't support for this statement, someone would need to release damage taken information and actually work this statement out, but at the time of writing I'm unaware of such data existing in a nicely compiled space for analysis.
