I dunno but I just can't do enough damage while also keeping my party members alive. I get that if it Wails, it will do Ice Breath next turn. If the heart is up, then it mirror sheilds but outside that the other stuff just wrecks me. Crushing Arm is guaranteed to kill at least one person, more if everyone doesn't max health. If Triple Bite hits twice on a person, they're also dead. It's all I can do keep everyone alive much less deal damage.
The elemental attacks or ailments themselves aren't the problem, it's the physical attacks still one shotting party members with the Max HP food buff. Ice Mist doesn't seem to do much to mitigate the Blue Heart end round party wide attack anyway but I can usually kill the heart before it's too much of an issue, even if it means losing all that DPS on the dragon itself. I'm already having to sacrifice so many turns to counter wail, both in terms of the ailment and the defense down. Using sleep resist rings kills too much of defense as well. The fact that it's doing so much damage makes thing I'm missing something but I don't know how else to reliable boost my defense or lower its damage.