Nothing stopping you from /assisting a PLD and killing the mob he is engaged with while super tanking the rest. This is actually beneficial for everyone. If the PLD can survive all the agro, and you can't - then don't get hate genius. Don't blame PLDs who can super tank for your failure to understand your job's limits and game design. This isn't abyssea where you have infinite MP and Atmas to make up for your lack of understanding and skill.

If a PLD diaga's/banshiga's all the mobs it is to super tank. Don't cast aoes or use horde lullaby (dumb brds) and then complain when 10 mobs falcon PAWNCH you in the face.