Were you really expecting that performance jump? This is a 380x replacement, and it's coming in at the same price as the 380x was launched at. ~$232. And you were expecting it to be faster than a 390x/980? That's more than a two tier jump in performance.
That is very unlikely to happen. This is the mainstream market. This is the market below the 970. If it's between 390 and 390x in performance that will be a huge leap for this market segment.
And are you surprised that it concentrates more on power efficiency? AMD has stressed this all along, the performance per watt was critical for them. VR performance, power consumption and that they were aiming at the mainstream market first, those were the things that they emphasised in their conference.
I think the problem is that when rumours of Polaris first came out, people assumed the Polaris 10 card would be mid range and were expecting it to be a 970/390 killer. Those expectations haven't died even after AMD saying polaris were mainstream and entry level cards. I mean if AMD had released the 390 and 390x replacements first, most people on this forum wouldn't have given a damn about the performance or price of the 380x replacement.