Exactly the same problem here.
Confirmed three R710 boxes, both with and without H800 and MD1220 storage.
One of them also has an MD-1000 DAS and disk performance is very bad (on VMWare 4.1U3 was good/acceptable).
Exactly the same VMWare ESXi 5.1 + OMSA setup works flawlessly on an R720xd for a few weeks now.
I have also a T410 which seems to work (not confirmed since it's too recent - but it does not have a PERC card, it has the el-cheapo one I can't remember the name).
Somehow this all seems to be related to PERC.