DPS is not viable mitigation unless the change in damage output from killing the mob sooner is greater than the damage that would be reduced by putting those stats into mitigation. It's not 100% mitigation, it's only the amount of damage that you shave off the end of the mob's life (and in my experience, tank DPS doesn't help with that in 99% of the encounters in this game). If 250 Parry mitigates .5%, but you killing it faster cuts out one auto attack that would account for .3% of the mob's damage output, Parry is the superior stat for tanking.
Now, if that autoattack would be more like 1%-2% of the total damage? Then okay, DPS stats are better.