I mean I'd rather do Gekko over Kasha in an exp party. Asuran Fists -> Gekko still makes a level 3 renkei, and Darkness is just as good as light, without the requirement for Tachi: Kasha.

Sure, the paralyze effect is nice, but that's what rdms are for, and I consistently get better damage on Gekko than I can with Kasha.