got the same actually XD running on a i7-3930k have 2 cores per vm since 1 core makes it stutter like mad. though if d3 process runs at "above normal" its gone; ah well XD
Thing is, you need some changes to windows file if you went to keep that setting saved. When d3 or whatever crashes and restarts with a relogger, then it will just restart in "normal". Other than that, you can indeed manually change the priority setting