(Cont because 3000 word limit sucks)
To speak to your suggestions.
WAR - I agree; simply make them a big health bar that can be filled easily due to healing augmentations; I would probably remove the 30% mit and simply give them a bigger health pool; I think the way "other" classes interact with tanks generally feels the "same" with the noteworthy exception of DRK. The idea is that Warriors use Bloodwhetting and their melee skills to replenish that HP deficit.

DRK - I would focus more on the TBN gameplay and remove its mana cost - instead I would have TBN generate a HP bubble that grows with your damage done (yes putting a upper cap on it) the idea being that the more damage and solid gameplay a DRK is doing; the bigger "encroaching darkness" or whatever the buff would be; creating new gameplay opportunities that at a glance look difference but really only upset the applecart slightly - while opening up avenues for DRK gameplay (such as shielding MT while working as OT without spending the valuable MP resource) I would go so far as to even make it function as a "explosion" when TBN gets popped. This would allow DRK to function as a "drain" without just becoming WAR and leaving Bloodwhetting alone.

PLD - I would focus more on the Shield block and Clemency gameplay - our confitieor chain feels very much like the Delrium chain imo and it feels wrong.

GNB - The "selfish" tank; that said I would like to see GNB survivablity have perhaps more of a trade off for its expected higher damage then it does. How you do that? Hell if I know - keep in mind every tank should be able to MT or OT every fight.