In fairness and justification to Passage of Arms, your team has to be behind you, and as a tank that usually means you are off tanking or the boss is just untargetable, and you can't actually do anything while in Passage of Arms meaning unless you super quickly snap into it in a 1 second window for raid damage and your group just happens to be behind you, cool, but that scenario is very unlikely to play it. The other situation being an untargetable boss, in which case it's just a QoL for 1 less cast of a party heal from the healers, but functionally serves very little purpose anyway. It doesn't make it any less fair for the other tanks just because PLD has 2, and Passage of Arms is balanced in probably the best way a skill like that can be balanced. Either it gets used fully because your party just happened to be right behind you when you were DPSing and you risked clipping a GCD to use it, or you used it in a way that's just a feels-good casting, or you sacrifice part of your rotation which is already timing-sensitive. I see it entirely as a thematic ability that actually has decent function, and I have no problems with that. It's good flavor that still has good function, unlike Dark Mind.