User blog comment:JmLyan/Ori and Sein, the Light of Nibel/@comment-3391671-20160602235421/@comment-7481207-20160604114610

Sein's gameplay role in the original game is practically only Ori's basic attack tool (although that comprises the majority of your damage output). Similar to Wolf and Valor, Sein is mostly a helper rather than a major part of the kit.

Although it being magic damage actually weakens the passive early game (base armor is lower than base magic resistance early on), its damage early on is still a bit too high as you said.