Blizz won't do anything about it because the other faction has ways to deal with it. If a 40-boxer is camping an opposing-faction AH, then he's in an opposing-faction city. A city that is easily reached via portals from Dalaran and Shattrath City. And the other Alliance cities have auction houses as well, which means that he isn't stopping the other faction from using the AH, just from using one of them.

So Alliance characters on his realm have two reasonable options-- head to another city to use the AH, or send out a call to all of those level 80s in Dalaran to hop into the nearest portal and help them. He's in an opposing-faction city, for crying out loud. Endless guard respawns and the opposite faction won't be 'trapped' there after they get tired and log off for the day. Take him down and camp him until he's had enough, or avoid him.

Now, instance portals... I can't help you there.