Raw Intiuition is only about 3% better than a PLD sheltron while a PLD doesn't have to give up their own personal mitigation to help another tank, in fact it thrives in this by being able to share its own cooldown. Lets look at all tanks strengths:
PLD: Best OT by a wide margin still. Intervention is extremely strong and is even stronger when you have split tankbusters like 3/4 of the fights (you could add leviathan but that's only 1 tankbuster so I'll ignore it.) Divine veil is better for the party in a shield sense because the calculation of the shield is baised off of the PLD's max HP unlike shake it off where its baised of the person who has the effect (meaning DPS/Healers get a weaker shield than the tanks). Passage of arms for more party mitigation. Finally PLD has a strong ranged capability unlike all the other tanks making it idea for fights where there are periods where you lose uptime on the boss.
GNB: on demand OT skill that's pretty good and doesn't need any job interaction but mitigates more than WAR, has a regen that can be applied to other party members. Highest damage and has a party wide mitigation that is stronger when multiple raid wide aoe's are used (ala Titan tummults/3rd phase).
DRK: Best tank for magical fights with Dark Mind. Invuln is tied with PLD when it comes to duration but can last longer if needed (downside is the dying without healing part). Again has a pary wide mitigation the same as GNB being exceptional when multiple raid wide AoEs are going out. TBN is a strong OT skill.
Now what does WAR bring to the table? It has Holmgang... which is only 1 minute shorter than LD now and only one of the fights seem to support Holmgang directly really well (Leviathan) but it also has the shortest duration of all the tank invulns. Shake it off is kinda tied with Divine veil but the tie is only because the WAR gets the sheild too, at the cost of a weaker shield for the group. Then there is the self healing which is... good for auto attacks? But its OT skill is still the weakest out of all the tanks only giving 10% and a heal that is halved to your target making the healing pathetic if you are using it for them and not yourself. WAR is designed 100% to be a MT lets all agree with this. Problem is that besides E2S and E3S ( both tanks are getting hit) there are points in each fight where that "self-sustain" means jack. If this was SB where WAR could hold a boss the entire time like E2S then WAR would be a strong MT choice, but it isn't. You need to tank swap and OTing is WARs blantant weakness. I would rather have a more versitle tank that can do both MT and OTing somewhat well. I want to see WAR get buffs to its utility. You want to thrive on self healing? Cool, remove the 50% reduction on the other target for start and split Flash and Raw so when you use one the other doesn't go on cooldown. Buff up Shake it off a bit more if you invest into it for a better shield. Maybe increase the duration of Holmgang to 7.