Sure, might as well give us a reason to use those skills more than a couple of times per expansion.
I'm not exactly sure what you mean. 2.0 WAR's issue was that it couldn't survive hits that PLD could without Stoneskin/Adloquium from healers. Increasing WAR's self healing wouldn't change that. They could have chosen to make WAR's skills increase max HP like Defiance and Thrill did, but I assume the devs chose % mitigation because it's easier for them to balance.
I'm not going to pretend like I remember what people were asking for 10 years ago, I assume people wanted a use for Wrath outside of Defiance and didn't want to have less skills when not in tank stance. I don't think swapping between Defiance and Deliverance is functionally any different to turning Defiance on or off, and the jobs weren't any more similar because of it. I don't think this is a valid case of homogenisation at all. DRK getting Grit with % mitigation is more homogenisation than that.
Like you said, people had different ideas for what Shake it Off could be. The devs chose to make it a party shield, but WAR players aren't at fault for complaining about a useless skill. Slightly related, the devs are also to blame for Berserk/Inner Release becoming a Requiescat clone. There are so many things they could have done (including let people get used to 4.1 WAR with no gauge loss), but I doubt a single person asked for it to give 5 Fell Cleaves in a row. I know I saw people complain that old IR made WAR do 6 Fell Cleaves every 120s.
Making all tanks require more healing doesn't mean forcing healers to spam Cure II on them, it just encourages healers to use more of their kit than just using a couple of Tetras and Benison. Balancing groups of enemies in harder content is a different topic anyway, I wouldn't assume it would just be the same as aoeing in a dungeon when there's things like A2S's vuln stacks and buff goblins as examples to stop you having a WAR tank and heal through everything.