Also disclaimer, I haven't owned a large dog, I've just read and absorbed a stupid amount of dog behaviour stuff because one day I do want to own a large dog >.>
It might be an idea to link you to good things in the dog's mind, rather than neutral or "not supposed to be here" which is what it seems to be right now from what you're saying? (As he's barking at you even when held back it seems a bit more than just a big excited dog that wants to greet you and makes me think it might be a territory thing if it's not solved by exercise.) That does involve you and owner being okay with you being somewhat involved in his care, and involve time and effort from both of you, but it might be worth a shot. (ex. training him with commands he's learnt, maybe helping feed him, stuff like that)
Also definitely echoing daily exercise here, that can solve a load of things. If he's not getting any, in what I assume is a student apartment with no yard, little space, and owner not being home for a large part of the day, it's... not a good place for the dog to be. If he's under-exercised, everything else is much harder, and it'll be difficult to ascertain what behaviour is due to his lack of exercise and what is due to other problems. Some breeds also need far, far more than just one walk a day - several high energy working breeds need more like two walks + mental stimulation (why border collies, German Shepherds, huskies etc. don't really make great apartment pets - or just even pets - unless you're a very disciplined owner).
Owner might or might not go for a shock collar, some people are vehemently against them even for large dogs. Regardless, since you don't seem to be part of his life much outside of being in the same area, getting disciplined whenever he sees you might not be the best idea - need to make sure that he can distinguish between you being there with him, and him lunging/barking at you.
Oh, and just thought of a thing, that might or might not have been tried yet - if she's been attempting to train him and had some success with some commands, you guys could work on you entering the common room with him there with her distracting him with commands and treats (rather than just holding him back), to teach him that you're not a big deal. But again, that will require work and time from the both of you. Is you opening your door a trigger/alert for him? She needs to desensitise him to that if it is.
And not sure if owner's done this, but often obedience training can be pretty generic. If she hasn't told them of the dog's specific problems and gotten advice and training specific to that, she probably should do that. They can probably give better help/tips than anyone here can.