I had the same problem trying to set up a computer, wasn't a mining rig, I was trying to update it from Windows 7 actually and ended up calling tech support.  It ended up being a bad ISO somehow, I had to download the entire ISO again. 

My 1080ti's I get 16.9 on 3 cards, so about 5.6mh/s each, running roughly 225watts apiece.  I haven't wanted to take my RX580s off Eth, nor have I bothered trying to figure out the sgminer fork for xevan yet.  If I do I'll update with it.

That's what it was, I thought I installed that driver to begin with but apparently something wasn't right with it.  

Yeah I used polaris, atiflash and atipatcher.

Mostly Hynix sadly, one Samsung and Elpida, I've got them all stable modded which is why I think it's the drivers.  I thought I installed the correct ones but I'll reinstall in the morning again.

I have a 6 card, MSI Armor 4gb rx 580 rig, using Claymore 10.2 I get 27-28mh/s in Linux, but I don't know Linux well and it kept crashing, I got fed up and installed Windows for the time being.  I get 16mh/s stock and up to 20.5mh/s modded, no memory errors.  

I am going to assume I have the wrong drivers, what driver works in Windows 10 best and if that isn't my issue any idea where to look?  I wouldn't be annoyed if it were 5% or so, but 25% is definitely something wrong from what I can find.

Bsod has found a couple but something isn't right.