The 780 didn't have competition for ages and now the 1070/1080 won't have competition till the end of the year. The main improvement of the 9xx series over the 7xx series was power consumption, so AMD could hold their ground against the 980 with the 290x performance wise, the next gen competitor by AMD released 9 months after the 980. Nvidia always has the new and shiny factor on their side for way too long and when AMD releases it's just the same thing for a bit less money.
Once AMD released their cards they were decent competition, 290 was definitely the card to have for example, but by the point it released and got viable nvidia was already swimming in 770 and 780 money.
The only thing AMD lacked was quite a big thing to be honest, the power consumption and temps were unacceptable, you know temps have gone too far when you need to ship your flagship card with an AIO by default. I'd consider that on par with the lack of DX12 performance nvidia is facing now, at least you can get improvements there with drivers and they don't really need to care for the next 6 months because there is no competition. Whenever nvidia is facing an issue on launch they have breathing room to fix it, AMD doesn't.
That driver decay thing i haven't heard of prior to Barnsley's report, my 770 didn't seem to lose performance. So unless i see broad range complaints i'll give them the benefit of the doubt on that one.
