Okay, this much has been decided: The dragon, upon noticing that his blindsense can't see into the hallway anymore (to be fair, he HAD mentioned he was watching for the hallway) realizes that you're back, and out for blood. He rushes over to the Wall of Force, and readies an action to breathe on you the moment the wall goes down.
You BOTH have readied actions to act the moment the wall goes down. Thus, if you take the wall down immediately, as planned, I'll have the effects go off SIMULTANEOUSLY. You take damage, but the disintegrate goes off.
Would knowing this cause you to delay your attack (hold wall of force longer)? I haven't gotten the confirmed druid revised action yet, but it may or may not be an earthquake... the dragon shouted orders to protect the mirror.