Knw.Arc. DC: 30.....Respen's Roll: (35) Success!
Judging by the strength and schools of the magical auras, and knowing so much (as you certainly do with a base +25 check!) about magical arcana, you can tell that the TRUE strength of this door lies in the situation where the door has closed shut. Much like an Alligator's jaw, once this door closes, it's going to be Hellishly hard to get open again.
However, the way the auras are arranged, you can tell that the door doesn't need to be held open AT ALL!
The mere presence of someone standing in the doorway is enough to keep the door open. You figure that it must be part of the trap; the door doesn't close until everyone is on one side or the other. Remaining open would certainly give someone a false sense of security. But once the spell detects a clear doorway, there is probably a countdown, after which the door slams shut, locking the occupants inside for good.
If someone, the twins, perhaps, were to station themselves in the doorway, they could keep the egress open; of course, guarding the door in such a stationary position would make them a BIG target in melee combat.