Arguably the Vega 56 is a good card for the price tho.
They're not bad in the same way a 980Ti is not a bad card and 2500K is not a bad CPU. Even today.
So AMD is finally making a high-end GPU (performance-wise).
It's just that this is not a product that was promised. Not a card we would expect in 2017 (looking at what NV can do).
In many ways this looks like a brute-force answer to the more innovative competitors - a bit like what Intel did with Skylake-X to counter Zen (possibly clocking it way higher than they originally planned).
It's just that the performance/power draw relations are even worse than in CPU battle. And of course AMD had literaly years to prepare Vega and it was meant to be a revolution. Now it looks like an interim solution and we're already beeing fed by Navi hype.
As some have already noted: a dual Polaris could be just as effective and most likely cheaper.
Or from another point of view: think how quick would Pascal be if NVIDIA calibrated it for Vega's power consumption...
And a couple important notes:
1) Just how bad will the Vega APU be? Is there any sense in making it? Will a ~30W Vega be noticeably faster than a ~30W Polaris?
2) Will we see a mobile RX Vega?
Vega is for the datacenters not for gaming rigs.
I don't know where you got this idea from.
This is not a computation card, it will not be used in datacenters. Not happening. Ever.
AMD is targeting RX lineup at gamers. They have other cards designed for professionals.