Kimontonkou has only 1% delay so...the only limit is her SP early on :V
Yeah, using a character for 18 floors seems "trying out" enough for me.
18F's single target is a direct upgrade from Spear, his speed and defence are good enough, his buffs allows early 20F/30F grinding and has a pretty good nature nuke as an addition so he can help out even against randoms.
Elder Dragon Jewel solves the recovery problem.
1st slot is usually China or 18F if I need to rush(Kedamagrammaton, Shiki, 30F), second is Reimu(she's durable enough to take most attacks), third either Ran if I need to buff or Kaguya/16F for extra turns and fourth is usually a nuker.
Yeah, I'll say it directly, single target healers suck balls. Reimu is all I ever needed.
Shiki can also be in the 3rd slot for stuff like 30F.