installed the suspected card in my Win 8 and it immediately booted a low res desktop. Nice! right clicked the desktop to set bigger res and immediately black screen and monitor complaining about not getting signal, same symptoms as on Linux so i guess i can safely conclude i fried that card. Did not do any deliberate overclocking or undervolting yet but maybe it was the 74 degrees / I=17 that did it. Anyway the cards were not making any ROI with BTC down (and therefore the alts as well), high power costs over here and running below targets.
My failures gpus turned off my computer and then when i tried to power on again the pc didn't turned on (but removed the conflictives gpus and pc turned on without problems). It was like if a short circuit happened with the cards, perhaps any capacitor but i'm not sure. Curiously i have other cards (same model) working always over 75º temps 24/7 during more than 2 months without problems so i can said than temps & voltage wasn't the issue.