There are numerous reasons why WAR OT is superior for T13, and only some of them have to do with tank damage (and PLD still mitigates far better). There's also keeping up Eye/Path fulltime as OT, which is impossible to do while MT while not losing aggro to PLD, and keeping Path up is important.
So let's recap:
- PLD takes significantly less damage than WAR
- WAR cannot maintain debuffs and hold aggro off PLD while MT
This is pretty clear cut.