let's break it down then.
invuln:
PLD (7m): true invuln with no cost
GNB (6m): true invuln with the remaining HP as the cost
DRK (5m): not true invuln, you'll keep getting damage when using invuln, but your GCD during invuln heals yourself a lot
WAR (4m): not true invuln, you'll keep getting damage when using invuln.
Tell me how it's not one of the worse invuln. if you want to survive after invuln as WAR you need to use at least one or two other of your healing oGCD. same as GNB, but at least as GNB if you get healed during your invuln, your HP won't go down. WAR on the other hand, any heals during the invuln duration can be wasted. the fact it has the shortest CD proves that the game agree that it's the weakest, thus they make the CD shorter to make up for it and make it's value on par with everyone else's invuln.
on-demand mitigation:
PLD: Holy Sheltron (50 gauge fills in ~25s): 15% (8s) + 15% (4s) + 250p 4 ticks regen. Can target party member.
GNB: Heart of Corundum (25s): 15% (8s) + 15% (4s) + 900p heal. Can target party member.
DRK: Oblation (60s) + The Blackest Night (15s): 10% mit (10s) + 25% shield. Can target party member.
WAR: Bloodwhetting (25s): 10% (8s) + 10% (4s) + 400p shield + heal. Use Nascent Flash instead for party member.
Just by the number itself you can see that WAR at the bottom along with DRK.
'Bonus mitigation':
PLD: Bulwark
GNB: Camouflage
DRK: Dark Mind
WAR: Thrill of Battle
All of them has different effects, can't really compare but WAR's is definitely not stronger.
120s mitigations:
every tank has 30% mit for 15s. no difference.
healing:
PLD: Clemency (1000p heal, can spam but cost GCD & MP)
GNB: Aurora (200p 6ticks regen, 60s CD, 2 stack)
DRK: None. But you can technically use Abyssal Drain if youre desperate. (200p, 60s CD)
WAR: Equilibrium (1200p heal + 200p 5ticks regen, 60s CD)
WAR is better than GNB & DRK here because again GNB & DRK are not sustain tanks. compared to PLD though, I won't say equilibrium stronger than clemency.
raidwide mitigation:
PLD: Divine Veil (10% shield + heal 400p) & Passage of Arms (15% all mit ~5s)
GNB: Heart of Light (10% magic mit 15s)
DRK: Dark Missionary (10% magic mit 15s)
WAR: Shake it off (15% shield + heal 300p + regen)
GNB & DRK are the weakest because they're not sustain tank. PLD's raidwide mit is stronger on the mits, while WAR's raidwide mit is stronger on the shield & regen
that's all. WAR has already been having less mits compared to PLD and sometimes GNB.
And no you can't conclude a job is higher DPS than the other 'depending on the timeline'. that's not how it works :')
and yes I know a lot about tanks, and I can confidently say I know a lot more than you
Well anyway I hope you learned something new now, you're welcome.