The problem with tanks regarding damage is that you can't make them deal dps that's too significant, otherwise people would catch on to the fact they can have good defense and still deal enough damage to carry a fight. Simple fact is that even if tanking was really in-depth a lot of people just don't like the role.

Also people underestimate pallys Off tank dps compared to warriors, warrior does beat pally in aoe dps and dps while in defiance compared to shield oath but a pally in sword oath using their skills correctly can OT dps about as equally as a warrior and i believe better (barely) on single targets.