Yep, it's dead, after only 1 year . It was an ASUS R9 270.
Cause of death: a VRAM chip died. Probably because it was around 33-37 deg C in my room at noon for the past week. Case is pretty well cooled however, CPU stayed below 60 deg C and GPU below 75, with reported motherboard temperature today of 36-37 deg C.
This means I won't be playing War Thunder until I get it replaced, luckily it's still under warranty so I hope to get a replacement next week.
These were the last pixels it displayed the last time I managed to boot it up.