Before gates go down, use blink. You will get trough wall and you will be able to AoE it happend to me. Rogue priest. Couldnt sap rogue got out of stealth ''ALMOST" lost.
I hope this helps some mage combos
{EDIT}
1 more nice bug. use /logout in dalaran sewers but remove it before you log out. you wil lstay upstairs