Re: Hmmm....
"In your dreams! The overall average performance gain is not going to be anything better than 10% to 15%."
If you count crappy integrated graphics PCs maybe. For high end hardware, 40% performance gain is realistic.
"And Microsoft was claiming a +100% to +500% improvement..."
Actually it's better than that for many use cases:
http://www.pcworld.com/article/2900814/tested-directx-12s-potential-performance-leap-is-insane.html