Also, Guran vocalizes just after he attacks. It's something like, "Oof, you Doof!" Anyway, his exclamation should be loud enough to be heard by the others in the antechamber room. Hence, if they weren't awake before, they should be quickly -- at least soon enough to act on their turns.
Edit to add: Guran doesn't move from his spot just outside the doorway. He's not sure just how he should act to protect the others, but letting the orc barrel into the antechamber before the others get to their feet seems wrong.