It's been beaten to death but I think it bares repeating. If your warrior tanking in coil, you are only putting more strain on your other tank and healers. PLD is just better at it.

I have yet to see a coil boss that is easier with a war than a PLD. The final phase of turn 4 is nearly impossible without 2 PLDs. One of the adds you tank as a warrior does not build wrath charges. If you don't have a bunch of melee dps to pop the knights to reduce incoming dps, it may just be impossible without luck/kiting. If you run 3/4 physical dps, you can try it but it would still be easier with 2 PLDs tanking.