You said it yourself. Critical hit.
If I'm not mistaken a 22k midare setsugekka should be a non crit-non direct hit midare. Since dragoon full boosted Full Thrust direct crit is 16k, and midare setsugekka without any buffs is almost double the potency of a normal non buffed Full Thrust, I'd assume that a crit midare should round 35k and a direct crit around 40k.
So yeah... they are op.