Red Arremer
Member
Is completing the story mandatory on each character? I know there are bonuses but do they matter
Not mandatory, no.
The bonuses that matter are the permanent bonuses to health and spirit and I think skillpoints, and you can play all of the game's regular content without bothering to do those. Only grab the rewards with the character(s) you actually want to get into endgame content, since then they're worth having. Beyond that, though, it's ok to ignore them.