I can see that having a bard, summoner, and dragoon all dotting out the nails could be a viable way to complete the nail phase. I imagine whatever your last dps slot is, it is the one that sacrifices their dps rotation to defeat the nails.

... Which is entirely my point. It seems that this strategy spreads your damage and takes even longer, due to the fact that you have to wait for dots to tick out and and take longer on the beginning nails (which makes things difficult for the healers / melee).

I find 2gcds or less by each damage dealer on each nail to be far quicker and far more manageable / simple / easier to heal as a strategy for that fight.

Spreading dots might increase YOUR overall DPS, but I find killing the nails quicker increases the groups overall DPS. The sooner the nails are dead, the quicker you can jump back on ifrit and the sooner the healers can refocus solely on the tanks.