Alright, so I feel like now's a good time to make a 2nd post in here to address some posts.
Defense: lol, Defense is not the problem. It does nothing for magic-based attacks and is not the same as % based mitigation.
I'll get the lols out of the way first. I'm going to give Mog the benefit of the doubt here and say he's being silly by suggesting that this is a matter of Defense. However, it does provide a good opportunity to clarify for some others who may not be so informed. Defense, just like most other stats in FFXIV, don't make a significant difference on their own as they are based on calculations that involve dLevel (dLv). When facing enemies that are significantly lower in level than yourself (a large dLv) stats become very effective per point, however when facing enemies who are significantly higher in level than yourself (a negative dLv), such as primals and various bosses, we find that they are greatly diminished in effect. I suggest everyone take a look at the extensive testing done by Kaeko and Seiken for the delicious number crunching.
Setting aside the fact that Defense does nothing in the way of mitigating magical damage, which tends to be what many bosses use as their most devastating skills, it is also greatly diminished at most endgame scenarios where we face enemies greater in level than ourselves. Going further into this, this thread is primarily about PLD as a tank vs WAR, and in turn overall class/job balance. Wearing more Defense is something a player can do both on PLD and WAR, and thus is not a solution to propose for fixing PLD.
Enmity: Tougher to hold hate on PLD, but overall very much possible to do. Ultimately not the problem.
There are various reasons why people have come to the conclusion that WAR holds better hate than PLD. Before I get into it in a bit more detail, let me say it bluntly first: Yes, as it stands, WAR has better capability in enmity generation than PLD. However, the solution here isn't simply giving PLD a massive enmity-generation buff. It has the necessary tools already, however it's primary tool for accumulating hate is not damage like it is the case with WAR. It's more about clever use of abilities and healing hate.
You see, WAR is not difficult. When tanking on WAR, you're actually just being a DD that doesn't manage enmity, instead thrives on it (sound familiar?), and you're going apeshit while you act as a damage sponge with your large pool of HP. In short, as a WAR you're just facerolling the keyboard. Just blarghwrwujyerrwuknfdv... so to speak. A PLD on the other hand plays more like NNGGGFFFFFFFFFFFFFFFFFFFFFFFFF!... as you try ever so hard to make sure you're following the right cooldowns, stacking the right skills, and more importantly than the rest, curing yourself with Holy Succor every chance you get to make sure you stay alive due to what little HP you have. It's hectic. So while it's more effortless and direct on WAR, it's much more work and less obvious on PLD. Right now, that may seem unjustified, unbalanced, unfair... un-whatever. What I see there is not a problem though, but an opportunity so to speak. There's a clear distinction between WAR and PLD as tanks. They're inherently different in style and use- or meant to be.
Now, as I said increasing PLD's enmity generation isn't the solution. It has access to Flash, Provoke, an Enhanced Rampart (which again works better when there are melee DDs in range to increase your hate generation as well as you increasing their defense. See the pattern here?), Sentinel, War Drum and 2 enmity generating combos. So ability-wise it's quite loaded with avenues of gathering hate especially in multi-mob scenarios. Its other primary source of enmity, healing, however isn't working as intended due to the simple fact that PLD takes too much damage to manage. For maximum hate generation, PLD should be healing other party members alongside the WHM. That's 50% more enmity gained from Holy Succor, and perhaps more importantly less enmity gained by the WHM. Double whammy! Also, let's not forget that 1.22 will be buffing the enmity values of materia, in which case it may just become common practice again for PLDs to prefer enmity-enhanced Winglets.
It's barely an issue now, and it will be even less of an issue with the materia reform and if they apply this %-based damage mitigation fix.
Health Points (HP): In most scenarios, taking less damage is more important than having more HP.
Taking less damage means getting healed less. It means overall greater safety and reliability. It also makes the tank easier to manage for a WHM. You won't see the HP bar value bouncing around like crazy as much as with WAR. Another benefit of being healed less by a WHM is that the WHM doesn't incur as much enmity.
Now, the important thing here is I don't mean to say that there won't be, or shouldn't be, scenarios where having more HP is more beneficial. I can even think of fights where having a DD-Tank like WAR is more beneficial even if PLD is to be fixed like this. That's not a problem though. The problem never was that WAR can tank, or tank well even. The problem is, and remains to be, that it can tank better than PLD in virtually every scenario. There are very few uses for a PLD right now and it's a shame. Having scenarios/strategies that prefer a WAR tank as well as scenarios/strategies that prefer a PLD tank is ideal. I'd go so far as to say that overall it should tip in PLD's favor, as it can do nothing but tank whereas a WAR is still a viable DD.
If you bothered to read inside the boxes, thank you for taking the time to read my obnoxiously long walls of text. If not, thanks anyway for your contributions. I feel that this is a very important matter in FFXIV and requires the proper attention, so I appreciate anyone who helps in that regard by providing healthy discussion and attracting the necessary attention to the topic at hand.
Note: I initially intended to post this on the PLD forums, however after thinking it through I decided on General, not primarily because it's visited much more, but because the post was relevant to the case of class/job balance and thus exceeded the boundaries of being a simple discussion of the PLD job.