I made a topic in the Steam forum. Most players agree that he still feels underpowered compared to the Devastator. This suggests making the Storm Bolter full auto, nerfing its damage to that of the bolter and making it spew out at least twice as much as much bolts as the Bolter's three round burst.
While giving Fex, Warrior and Thrope "Armor" that reduces it's damage to make it balanced. Ie the only units that have that kind of defense. Otherwise they might die in seconds.
http://steamcommunity.com/groups/exterminatusgame/discussions/0/630802979414674964/