I have two Win7 x64 VMs (4GB Ram, 2 Cores) running and I am still able to play PoE on my native OS without any felt fps impact (i5 3500k, 16GB Ram, HD 7870). I have tried to run the VMs with 1 Core but loading times get pretty long and the clients tend to crash during loading screens.If you didnt do it yet, set the PoE Texture Quality to 4 on your VM clients and use vsync. Maybe that helps.
And yes, I have those graphics glitches too
Does anyone know if it is save to create a network share of your PoE dir on your host OS and use this client on your VMs too? Is there something like a unique ID to a client installation?