During late ARR, that's how WAR played. You'd use Inner Beast from the gauge, it did damage AND gave a 30% or 40% mitigation for 5-6 seconds or so. In other words, you had to actually plan out when to use abilities. And IB was on a GCD, not oGCD like every other mitigation WAR (and other tanks) have.
The lack of identity is only one thing that is an issue. But I think the bigger issue is the ease of playing a job like tank. Tank stance gives you so much hate that 2-2-3 Fell Cleaves at the beginning of a trial/raid/etc is enough to hold hate for the entire battle if you just turn it off. We have so many mitigation tools, it is easy to just use more than you really need. Healers used to have Cleric Stance. They had to actually think about when they could focus on damage and when they had to focus on heals, since it was a 10s cooldown to switch. DPS jobs had a button they had to hit occasionally to shed hate.
Many MMOs have tank mechanics that require a tank to think about how to use their abilities to keep hate and mitigate damage. Or communicate and collaborate with the party to do so. We are just 8 players playing 8 separate jobs at the same time in the same area when we do a raid/trial/etc.