Having now read Carbon Copy, I can see how it could be a killer. The enemies in that are pretty tough. I actually thought the fight seemed pretty easy when playing through it, but that's because we sent a wave of drones in first as sacrifices (which was expensive) and we were able to get the drop on the enemies with some pretty heavy firepower.
Ashes absolutely gets nasty, although due to using some remote firing platforms (much like the drone strategy) the fight at the end wasn't as deadly for us as the fire.
Dangerous Games #1 we got through without even firing a shot, so it's hard to gauge the difficulty of the fights.