1. You're right that strong upsides are much needed, being against one skill doesn't mean I'm against the idea of jobs having strong upsides, though theirs going to be instances where i genuinely do disagree, theirs still a extent to where a job needs to be balanced and feel good to play with.
2. Rotations are very important to gameplay and should be made unique, they can be a unique thing every tank is builder spender burst they follow the same pattern and while just slapping on a unique rotation and calling it a day isn't the full solution its a Major part in the puzzle on how tanks feel very samey, Why's their no Procs on any tanks? why are there only generic 1, 2, 3's? ect. These things being addressed helps majorly with making tanks feel unique. Healer would also benefit from this because healers deserve similar treatment in gaing actual variance in damaging skills, infact the situation with healers is more dire on that front.
3. You can say tanks can have a equivalently strong upside, but in reality what would that even look like? how would this upside both not matter in high end but also feel strong and unique in the content that makes it equivalently strong, again it just feels like your trying to justify bad design because it's "unique" if Gunbreaker could one shot random dungeon bosses sometimes that would be "unique" but it would blatantly obviously be unique in a bad way, such as Warrior becoming Immortal for 8s in a down time of 17s in AOE situations in inherently a bad design. This isn't just "unbalanced" this is egregiously unbalanced in AOE situations. I even suggested maybe instead of putting the mass AOE on a 25s cooldown, It might be a bit more fair on your 120s that way you get to feel "OP" every 2 minutes for 15s but not be completely immortal and not even need a healer.
4. The problem is both universal and Warrior related, yes we have too much mitigation and tanks not taking enough damage, but the point is even if we fixed that blood whetting would still be a massive outlier and a issue, If we want tanks and healers to feel relative and contribute to helping each other, rather then tanks just doing the healers job.
5. Dungeons are designed in a way that will likely never change It's a even more unrealistic ask for them to change dungeons for the sake of making warrior balanced rather then just not making its AOE as broken. Even if they changed future dungeons Warrior would still be "op" in anything once it gets its short CD to 100.
The way I see it is, you made this conclusion that if your against skills like bloodwhetting you must be pro homogenization, when that's simply not the truth you can be in favour of homogenization for one skill while bringing up the design and uniqueness on different levels. No matter how against homogenization I am if something is that egregious to me I am not going to defend it just for the sake of it.