Let me correct you on some stuff here bro.
1) A defective card is just.... that, a defective card. Nvidia users have the same problems. That's just luck.
2) Where are you getting the Vega below 299$ information? This is flat out wrong. A RX 580 goes for 270$~ (the binned skus) , and it's been all but confirmed that Vega will only launch in the high-end market first. Expect a 500-600$ RX Vega w/ 4096 SP and 8 GB HBM2. Polaris is the mainstream lineup for 2017 and Vega will only replace it possibly after Q1 2018, because those were in their investors conference slides.
Also the 1070 will set you about 400$ , a 1080 will be 500-550$. And why will AMD release a 299$ Vega gpu (these are big dies mind you, not smaller ones, you can't come out sell 400-500 mm2 dies for 300$ without incurring serious losses /bad yields) and shoot themselves in the foot with the Polaris lineup? This is not logically what I think will happen.
EDIT - Just did some looking up, the SC Black edition is somewhat cheaper because of a cheaper shroud design and no backplate. So there's a tradeoff , how much does it affect you, is upto you. You can probably pick up cheap 1080's for 500-520$ ( Total cost 620-640$ ofc).
3) If you're just playing OW on anything below 1080p 144 Hz, you're completely fine with a 1070 / 1070 class card, even an RX 580/ 1060 is more than enough.
Make the smart choice
All the best.