Creating content that leaves no class out is hard to produce since players will always find themselves going with the strat that makes things the easiest. When it comes to PLD/WAR tank issue I do see the issues since the games concept is designed on dealing damage throughout the battle, but Paladin goes against this since they sacrifice the damage they are able to deal to reduce damage taken and act as more of a support. However in content where you need 8 players for x event the abilities which PLD offer are not as needed when you can easily grab 2 WHM to support the Warrior that's tanking with their ability to cure large amount as well as WAR's natural High HP.

I think the trick to fixing Paladin is making it where they sacrifice their enmity to dish out heavy damage while attempting to balance those abilities while still being able to hold hate. A warrior's gimmick is basically dishing out heavy damage and using abilities to heal himself through battle while having support from mages and throwing out defensive abilities and voking when needed.

A Paladin is suppose to take less damage and support those around him but it doesn't help to improve the overall flow of battle it just helps alleviate any damage that might be taken.

Let's take Cover for example. 8 yalms isn't really that far so it might work on a DD but overall it's effects aren't useful with the current flow of battle. Rather then have an ability that can redirect damage for one player perhaps Cover could be changed to
"Holy Shield"
-Produces a barrier reducing damage taken by all allies (excluding user) by 25% and redirecting it to User, Effect wears off upon using Spirits Within-

Then change Spirits to this
"Spirits Within"
Deals Dmg, increased when "Holy Shield" is active. As well as change the combo action to have dmg influenced by current enmity rather then current HP.
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Hm, I can't think of where to fit enmity reducing type of moves but I think the above could improve some of PLD's capabilities but the other idea is this.

When it comes to the two defined as tanks,Warrior is one that takes hit so they should have the higher of physical damage taken however their constitution is weaker to magic. While Paladin can take better defense towards magic but they aren't as good as taking a physical hit unless they block it.

In a sense I see this
WAR=80% physical dmg taken, 130% magic dmg taken
PLD=100% physical dmg taken, 70% magic, 50% physical dmg taken with shield.

Then how about changing the following 4 abilities,
Aegis Boon=Improves block rate by 25% when active
Phalanx====10% chance to improves block rate by 25% for 5 seconds
Shield Bash=Improves block rate by 25% for 10 seconds
War Drum==Improves block rate by 50% for 10 seconds

I'd like to think with the slight change to these 4 abilities one may see a change to the amount of blocking they do on Paladin

Maybe as a last change, instead of the lame ability that Tempered Will offers now change it to one that influences shield block rate.

Keep the 180 recast but make it where it increases you block rate by 50% for 60 but negates you from being able to use shield counter abilities or shield bash while active. The idea then would be that Tempered Will focuses you on blocking but then you sacrifice your ability to use skills that require a shield since you're more focused on the mob rather then using your shield as a weapon.
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It's hard to say, perhaps the above could work in reducing the amount of dmg a PLD takes while slightly increasing their dmg but not so much in a way that it outshines WAR.