I've said it elsewhere and will repeat it here: Vega dGPU is hardly a high priority for AMD. Their priorities must be something along these lines:
- Zen as Server (Epyc)
- Zen as APU (TBA)
- Zen as Ryzen
- Other things (Vega dGPU, Threaripper, etc.)
Thing is even when AMD had the better product (5000 series, arguably most SKUs of the original 7000 series, Hawaii versus 780), they always sold way less than Nvidia. So in terms of return of investment, dGPUs are hardly going to get a large R&D share.
By far the most important thing with Vega is how well it performs in the Zen APUs and it's unknown whether getting it to do so will be a positive or negative for its performance as a dGPU. The other unknowns is whether RTG made good decisions with their insistence on using HBM2 and also whether they made a part more suited to HPC than gaming. Obviously, they can't afford to make both unlike Nvidia with GP102 and GP100.
As for 300W, well that sounds like it's running way outside it's sweet spot. Only now with Ryzen do AMD hopefully actually have volumes for their GF wafer agreement, but a big question always why they didn't use GF for GPUs previously. GPUs should be easily to either be wide&slow or narrow&fast, so all these years when they paid the penalty, why didn't they make bigger dies and run them at low clocks. (Hawaii had way better perf/area than GK110, but a larger die running slower would have made more sense; certainly underclocked and undervolted, Hawaii was actually rather efficient.)