Update: I installed older 17.10.2 drivers, and after two days of intensive testing with games and mining it yielded no issues whatsoever. It seems I'll be staying from the Adrenalin drivers till they are ironed out. Those gave me random system crashes on the desktop with the RX480, and this glitching with the Vega. But interestingly, the blockchain driver worked with no issues on the 480. I don't think its too early to celebrate, but regarding I didn't see any glitching in the usual scenarios, like alt-tab from the Vanquish menu, I guess its fine now. At least I don't have to return the card, because with the current stock the only thing I can get in return is my money.