Originally Posted by
pandabearcat
I would suggest it may be a dps increase, however iirc you don't even have tri disaster up for that phase for 30 seconds (if assuming you tridisastered the carapace, which I don't see how you can do damage to it unless you did). That phase lasts at most 130 seconds, so if you have 100 seconds you may have time to use it twice, while losing all the AA damage from ifrit. I think I'll pass on that, for 30 seconds of more dots (if that, they should be dying much faster).
Furthermore, the mana cost of summoning means unless your bard is playing Ballad you will likely see a higher dps increase casting more Ruin II and autoattacking or throwing some nonDT Ruin III.
Just hope you're lucky with choosing which one to dot.