There are three tanks. You only bring two tanks into 8 man content. One tank will be considered "worse" than the other two, even if it is the most insignificant reason, by the people seeking to bring the best possible team.
Using Omega Savage as a lens in which to view the tanks, we saw many groups take PLD/DRK into early prog, as the community had deemed WAR's lack of utility a dealbreaker, and brought DRK instead. Not to mention WAR had been somewhat clunky until they patched it the same time Savage was released; many people had already planned on bringing DRK, and it wasn't until the WAR changes were learned did we start to see the community shift from PLD/DRK to PLD/WAR. Fast forward a few months, and the most active threads I see here are the "DRK Feedback" and "DRK as a Niche Tank" threads.
It's true that the WAR buffs (and lack of DRK buffs) caused this shift. I don't believe that any amount of "balance" will ever allow the community to see 2/3 or even all 3 tanks at the same level of performance.
TL;DR
The community will always find a way to dismiss one of the three tanks when you only need to bring two tanks.
I hardly call slashing resistance down utility, but it is.
I think what I want more than anything on WAR is to be able to "make plays" like PLD can do with Cover and DRK with TBN. When our group practices speed runs, we will occasionally have an oopsie where our PLD can "save" the encounter with cover (think Earth Shaker on Neo). Or the other night on some V1 speedruns, our PLD dropped super low while healers were burning.
On PLD or DRK, you have the opportunity to use your kit and make a save. When that happens on WAR, I just keep swinging combos and think to myself "oh well, hope the healers and PLD can work this one out" as I go back to tunneling on gcds lol.
I'm saying that I'd like the have some kind of "play making" utility I can use on WAR.