Why do you think attacking is the best strategy? You are the one moving away from cover or concealment to advance against opponents who may have taken up cover or concealment.
Going down a hallway is walking through the 'fatal' funnel. I'm just a FOG but in all my FOF - walking down a hallway towards folks with guns who can 'pie' you - esp. with more than one opponent seems not a good idea.
In class, the 'house clearers' (unless they were a trained team - and sometimes them) usually got killed.
I also opine that a standard door is not cover. If I were determined to 'get' you and could discern you are by the door - I'm hosing the door.