The driver date has some impact, but not as much as you think.. I posted the latest benchmark of Civ 5 on Anandtech in the old Mantle thread:
Here you see the same thing. The GTX 580 is only 1% slower than the 7970. If the benchmark had used a lower resolution, the GTX 580 would be ahead I do not doubt.
That's what DX11 multithreading does, it removes CPU bottlenecks. The 7970 is a faster card than the GTX 580, but because it doesn't use DX11 MT, it's handicapped.
The biggest problem with DX11 MT is that it's performance is wholly dependent on the drivers. The time it took for NVidia to come to grips with DX11 MT turned off a lot of developers, and AMD of course still to this day haven't implemented it.
For example, here is what a Capcom developer said back in 2010 about DX11 MT:
Source
So much of the frustration by developers towards DX11 MT came from it not even being available for a long time. And even when it's available, it may not necessarily work as it's such a difficult thing for IHVs to do properly and fine tune.
Dice would have used it if it had been available when BF3 came out, as Repi lamented. As for Crytek, I doubt it would give them much benefit as Crytek games are always heavily GPU bound, and they have exceptional manual threading implementation anyway with CryEngine 3. Crysis 3 is the most GPU bound game I've ever played personally speaking, but it uses the CPU very well...
Using DX11 MT doesn't automatically guarantee a large performance increase, much the same as with Mantle. The performance increase is proportional to how CPU bound the game is..
That's why Civ 5 gives such a hefty increase with DX11 MT. BF3 MP likely would have benefited from it, but we'll never know I suppose.
The BF3 slides said that they were still waiting for the drivers. And after NVidia came out with their driver, I think he said it wasn't effective.
That was years ago though. NVidia's DX11 MT algorithm has surely improved considerably since then..
AC III also uses it. The 650 Ti Boost is a much slower card than the HD 7870, but here it's pulling even in this CPU dependent benchmark. Same thing with the 7950 boost and the GTX 660: