The only thing tested for mining with Vega is the Frontier version, it did bad, something like 30MH/s @ 300watts OEM VBIOS. But, the FirePro Polaris series also does poorly. Both of these cards are workstation-grade and were released before the gaming consumer versions.

Saying Vega is crap when only seeing test results for the workstation/server version targeted at AI, deep-learning, neural-network data mining, is like saying the RX 470/480/580/570s are going to be crap based on the results of the AMD FirePro release.

Even before the RX 500-series was released, miners started selling the RX 400-series based on rumored architecture and estimated hashrates before anyone had test results. Those miners then paid for new 570/580s and their hashrate and power consumption didn't change.

Vega still has a chance to prove itself in mining once some RX Vegas come out. But, I wouldn't go selling all your current cards betting on Vega being "better."