I was soloing and partying on birds last night and was having some real problems with Dark Spore damage. I know that one of the modifiers for Dark Spore is the mob's HP, but it seemed a lot more inconsistent as I used it.
I was saving TP for Dark Spore so I could use it while the mob was in its higher HP around 75%-95%, but it seemed like 4/5 times I would hit it for a consistent 45-49 damage while 1/5 times I would get a nice hit around 600 damage. I tried it out on varying days and the damage ratio was still pretty much the same whether it was darksday or lightsday or whatever day (It did do more damage on Darksday but the ratio of 1/5 "nuke" damage stayed the same).
I also tried to keep up with what kind of buffs or debuffs were used when partying and Haste Samba was mostly used, with an occasional quickstep- although whether Quickstep was used or not didn't seem to affect it either. Is there some other factor to the damage or is it just incredibly random?