The doors in the game are buggy right now. If you open them and then they go off of your camera, when you come back to it they will still be open but visually they appear to be closed. You as the player can walk through doors that appear closed too because in reality they are open.
But not always. In the shattered Sanctum I had one of the goblins attack Wyll through a locked door. And when I tried to leave the temple, I was attacked by the guards at front through the closed door. and that dorr was closed, because a) I couldn't hit back, and b) I actually had to open the door to counterattack and walk through it. The golbins just waltzed through it, though.
The doors currently make for some interesting surprises.