On the contrary; in combat, the main engineering section is one of a number of hotspots for activity. Power needs to be regulated, for one, lest the EPS conduits for the Steel Avenger blow. Engines need to be monitored and adjusted as needed, so they remain at peak efficiency during combat. Reactor core needs to be constantly monitored, even when the ship isn't taking hull damage - combat can strain the core, even a core the likes of which reside on the Steel Avenger, as everything is drawing power at once - shields, weapons, engines, life support. EVERYTHING.
So even though Vosur isn't on the front lines of orbital combat, he still has a critical role to play.