These two examples you gave were the exceptions, in the rest of the games, 7970 was well ahead of GTX 580. Besides GCN was a complete new departure for AMD from VLIW, some kinks had to be worked out. Vega is NOT a new architecture, it's new iteration of GCN with some major features added in, but the baseline remains the same. Maybe in new games it will pick up some performance courtesy of RPM, better handling of geometry ..etc, but don't expect sweeping changes in already released games.
Did you actually
read the GCN launch review? Those results
aren't exceptions. There are games that paint a bit of a better picture, sure, but there are also many others that show both cards similarly close. And even then, what we're looking at is the improvement relative to launch.
Besides that, you're blatantly goalpost moving at this point. You're the one who asserted that a 20% gain due to drivers is unprecedented. Now that that's been shown as incorrect, you've changed your argument to something along the lines of "Vega won't see the same improvement as Tahiti because it's a smaller change." Well, no doubt. VLIW->GCN is obviously a larger architectural change. No one is saying that Vega is likely to see the same 35-40%+ gains as Tahiti even though the current drivers are obviously immature, and even though Vega is the most significant change since VLIW->GCN, no one is arguing that it is a
greater change. I don't think anyone, as far as I can recall, is even going as far as to say that Vega absolutely will see a 20% improvement. It's
you who is saying that Vega
absolutely will not, and then insulting the more rational people who don't deal in silly absolutes on top of that.
There actually isn't any harm in admitting that you were
wrong on the internet, by the way.