FYI,
I got a "pure virtual function call" exception while playing City of Ash II normal mode. I believe other people have had problems with this dungeon crashing the client as well. We were past the bridge where you get swarmed and were going around the lava lake to the left. The crash happened during a small fight with some trash mobs. I was experiencing some lag during combat - maybe 500 ms. Seems odd that my client survived the hoards that swarm you on the bridge, but went down in a small fight later. Task manager showed the client was using about 3.3 GB of ram when it died.
System: Windows 10, 64 bit, i7-4770k, 16 GB ram, GTX770, nvidia drivers 372.90