As long as DPS is the only issue and tank can survive tank buster in DPS stance and stat like parry is useless. The less than 1% hardcore raider will only bring the best DPS group they can figure out of the job available.

Thread question is "Which tank is better MT?"
The best answer IMO is going for what SE designed the class in the first place.

PLD is design to tank heavy physical boss
DRK is design to tank heavy casting boss
WAR is design to be a soak tank with a high hp pool

If they release SAM. It will be a high dps tank alternative to the raiding auto include WAR off tank.