Hi,
What is your RAID configuration on the P2000? Is your datastore spread across all disks? Ideally you'd like to have a datastore across all of your spindles.
One idea I can think of is for you to Storage vMotion one of VMs suffering the latency to the local disks of the ESXi servers to see if it helps.
Eyal Traitel
Director of Marketing
Reduxio Systems, http://www.reduxio.com
c: +972-58-7300-749