Yeah if one of the tanks do not stun i try to do so, only thing that takes a huge chunk of my health (being bard) is his move after the nails were the entire screen is lit (Hellfire i think)
I do not think eruptions are needed to be stunned everytime. And for nails, 2 words to solve those, blm lb. 3 bars and a black mage can wipe them all. The other day we had 3 blm's with us, it was great