Performance Issues Running VMWare 3x VDI Guests

Is anyone out there running VMWare 3x with VDI guests on a CX? We are experiencing heavy writes for a 1 hour period M-F. This is causing Dirty Pages 99% and high forced flushes on Luns. We've tried every Raid type and Meta Lun configuration, including lowering the watermarks to 30/50, and still we are killing the write cache on the array. We are open to any suggestions you might have regarding VDI in general, or VDI on a storage array. Thanks!