Radan,
We're having problems with our MSA 2052 in RAID 6 in a way that is similar to what you described when yours was set up with RAID 6, and you said that switching to RAID 10 fixed it for you. Are things still good for you? Our MSA 2052 was fine for months until it suddenly turned wacky - sometimes really fast, but far too often it's horrifically slow. When we make a configuration change it seems to be fast for a while, but then slows down to a small fraction of what it's supposed to be. I can move all VMs off of one disk group that's slow, save one left for testing, and that disk group will still be dog slow. Like... dead dog slow.
Unfortunately, switching from RAID 6 to RAID 10 is not a budgetary option for us right now.