So what exactly IS the issue with Warrior?

[Maelwys]

That's why in my comparison I take the party composition as a whole. The only combination that seems to match perfectly is Warrior with two healers vs Paladin with one healer and one DPS. Things I looked at are, Party DPS, Tank Survivability, and class mechanics.

Without going back (again!) over the reams of math... exactly how "endgame" are we talking about?

Taken in a vacuum, PLD needs less healing when taking prolonged heavy damage.
WAR can self-heal medium spike damage and be pretty much immortal versus light damage.
They both do very similar DPS (assuming identical gear + stat distribution) but WARs are more self-sufficient than PLDs when geared for +DPS.

Taken in a Party context, the ideal endgame 8-man raid group has two healers: one SCH and one WHM.
Amongst other things, a big reason for this is because SCHs shields don't stack. It basically gives the best balance of damage prevention before a big hit and ability to top-up HP again after that big hit.

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+ SCH gameplay allows them to deal high DPS (via DoTs) alongside high Healing Output. In extreme situations they can go full healing and micromanage their fairy and just ignore DPS, but for the most part they can get by in Cleric Stance (for DoTs) using Lustrates and their fairy.

+ WHM gameplay requires them to choose a focus: ST damage via light DoTs and AoE Damage via Holy, or Healing (they can still do a little DPS when healing, and a little Healing when DPSing; but it's largely one or the other - aside from "Benediction" which recovers the same HP even when Cleric Stanced, and "Regen" which can be cast before stance swapping).

Taken together, you're virtually always going to have the equivalent potential of EITHER 1 Healer + 2 DPS or 2 Healers + 1 DPS (via your Healing Classes, in 8 man groups).

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That's where the issue lies - PLDs generally require lower healing due to their mitigation cooldowns, so for easy or medium difficulty content the WHM can switch to DPS mode. For HARDER content like bosses, the WHM can run in Healing mode and give the party maximum capability to "Turtle Up".

For WARs, they require virtually no healing on "Easy" content due to self-heals, and on medium difficulty content they are roughly on par with PLDs, but for Harder content the Healers won't quite be able to keep a WAR up for as long as they could keep a PLD up (so if the brown stuff REALLY hits the fan, the WAR party has less capability to completely Turtle up).

Therefore, for your comment "The only combination that seems to match perfectly is Warrior with two healers vs Paladin with one healer and one DPS": the average 8-man party with a WAR can already have "two healers and one DPS" - with both SCH and WHM in Full Heal mode - but they can effectively swap a Healer for a DPS on demand via the WHM swapping to Cleric stance. Conversely, the average party with a PLD can already have "one healer and two DPS" - with the WHM in Cleric stance - but they can effectively swap a DPS for a Healer on demand via the WHM swapping back out of Cleric stance. Now... at endgame, what situation is more likely: suddenly needing the equivalent of another Healer, or suddenly needing the equivalent of another DPS? (And bear in mind that the Tanks can ALSO swap out of Tank Stance to contribute more DPS in certain situations!)

Yes, you could bring another WHM. But even if the two WHM work together perfectly and the tank is never overhealed, the DPS tradeoff hurts the average party way too much - the optimal 8-man team healer combination is widely known to be 1 SCH and 1 WHM (or if you're really stuck, 2x WHM - but there's less effective HP without the SCH and thus less margin for error).

If you're talking about 4-man dungeons, then PLD + WHM is virtually always going to be the better option than bringing a SCH or a WAR from an efficiency viewpoint, purely because of Mob herding + Holy Spam... but realistically unless you're speedrunning, none of the classes should struggle in the slightest...