I didn't think it was too dark. But I played with gamma 0.5. Never used idgamma, don't understand what that effort is about. Fitzquake has a command called gamma, use that.
Nice with the bobs hunting me behind breaking boxes. Found one secret. Lots of nice details at places. The plaques helped a lot when trying to hunt down some places. Sometimes hard to see the color of the enforcers with them standing in the colored lights at ledges...
At a few places there were cool gameplay things like when you came to a clearing and spotted a bob on the left, started firing at it and then a fiend came from the front. So the bob was only a distraction.
The sentinels are pretty nice enemies in that they don't have such huge masses of health.
I was in trouble at places since with fitz I have to choose either a good res or dinput. I played this without dinput then and that means mouse acceleration so I was shooting all over the place. Also took off crosshair to make nicer screenshots. :)
Here's one (ran with xnview's auto contrast)