Selene's Web/Veteran City of Ash/Veteran Elden Hollow - these are the major three culprits right now. I'm yet to run any of these dungeons where one (or usually more, if not ALL) of the party has been frozen and forced into a manual quit and restart.
This is disturbingly bad right now... some of the achievements (like the no death runs) are impossible to achieve since everyone freezing results in certain death... I was hoping a 5 hour maintenance might have meant that it would get fixed... but looks like the PVPers got their candy once again this time around... can we STOP all the PVP pandering please? The game's backbone is PVE...