Some good information for any GM out there, just remember, not everything is designed to go against a player. Players who pour over the game's mechanics will figure the ins and outs to do crazy **** (SAME AS EVERY RPG OUT THERE!). Also don't forget that you can go to any of the 40k series RPGs and pick stuff up, they all can cross over to each other to get more information more things and new tricks.
My GM ended up hating the party because he had to end up creating creatures to throw at us from the warp because we broke the system BADLY, combine that with the fact that we where just incredibly lucky with dice rolls when we needed it. Face it, no matter what we're looking at here and how much someone has their fan gasm about something being unbeatable or the like, unless they're up against the full fledge power of a god not just a greater manifested deamon there is always a chance of success even if it's very small. This is the nature of RPGs, if a player dies, they die most players won't care in a setting like 40k.