_{the characters all have armor that ranges from 4-6, their TB are all between 3-6. This means that they can take between 7 and 12 damage without flinching. the weakest of them has damage reduction of 8 which makes it hard for me to really threaten them with ordinary grunts with lasguns.}

Well then your problem is that you have freakishly powerful characters with extremely good equipment that the adventure was not designed for.

For some reason I was under the impression that this was a starting campaign with starting characters. It's impossible for a starting character to have a 6 TB if it's not an ogryn.

_{the characters all have armor that ranges from 4-6, their TB are all between 3-6. This means that they can take between 7 and 12 damage without flinching. the weakest of them has damage reduction of 8 which makes it hard for me to really threaten them with ordinary grunts with lasguns.}

Well then your problem is that you have freakishly powerful characters with extremely good equipment that the adventure was not designed for.

For some reason I was under the impression that this was a starting campaign with starting characters. It's impossible for a starting character to have a 6 TB if it's not an ogryn.

Additionally; Severyn Dominate troops will have support weapons themselves! I doubt very much that your troops are going to just shrug off hits from a Heavy bolter! (1d10+8, pen 5) nor will they much like being set on fire with a flamer! Remember: The Severyn dominate are essentially IG troops and have the same basic equipment as their counterparts! Of course if your players are REALLY annoying you, Let them be the point squad when enemy Chaos Space Marines come calling!( Enemies of the Imperium pg 114 .) If your players are as BA as you say, they have no business going against "standard" mooks anyway! The old saying goes: To whom much is given, much is expected! There is also the very real fear factor if the players encampment is attacked at night by, well, anything! Carapace armor is worn much like medieval plate and doesn't just put itself on when a character is sleeping! (Figure about 1 minute to throw it on in a hurry but that's 10 rounds!)