From a healers perspective, mind you I'm still not maxed yet, the main downfall of warriors right now imo is that they favor health over mitigation. Historically, this is never good. When stuff hits the fan, and efficiency takes a back seat to healing output. Warriors are nothing more then a drain on healers mp.

To address this warriors will either want more self healing through tools of their own, or a passive to increase healing taken as a whole to make up for the difference.

Secondly, warriors have issues with crowd control. They can't maintain flash which is the only aoe threat you can do on cc, so naturally, more cc breaks and they take more damage. They need some sort of standardized warrior shout ability that will generate threat, do no damage, and possibly also reduce enemies physical attack power. This could could also help address issue number one on the list.

Honestly, there should be a solid reason to want one of each tank in your groups