Just wanted to chime in here, I've had pretty good luck with my cards overall, but am questioning one card in particular.  All of my cards are MSI Armor 4G oc's, most are SK-Hynix, but I have 2 that are Elpida, one of which is particularly weak.  I originally pressed forward with my normal vbios mod (one-click mem, undervolt everywhere), but was shocked to find I couldn't hit even 2000mhz without instant failure.  So I reinstalled the stock vbios, loaded up a miner, and began to tweak my overclock.  Seemed to be holding 1950mhz mem; at 1970mhz it would die within about 30 seconds (again, this is STOCK everything). Anyways after fiddling with it for a few hours, I gave up, and put my modded bios back on there.

Long story short, I have 1200/1920mhz/900mv stable on this card (easily my weakeast) at 830H/s cryptonote, anything higher would result in incorrect shares.

Could I really have been this unlucky in the silicon lottery?  I was reading multiple places, people were hitting 2000mhz on Elpida memory.