It doesn't need a DoT for the sake of having one. It needs more oGCD insta-casts, and some of those should generate mana. Plenty of Black and White magic spells left to make oGCDs out of. Verblizzard, Verwater (yes, I will argue this is White Magic-related thematically for FFXIV), some single target and some AoE, no need for a DoT in my opinion.