Had the same issues it has to do with the newer cards boosting/decreasing their clock speeds all the time. Go back to an older card that didn't have the boost feature and it works fine.
Also monitor your card with MSI afterburner or something while playing the game you'll see the clock speeds jump all over the place.
Crysis 1/cry engine 2 are one of the few really optimized engines that pull everything from the card that it can give and it really shows how boost clock is bs. It never boosts in times of actual need, just boosts when you are looking at things that already give you higher frames.
You can try this in modern games too, same thing happens but the clock speeds don't go all over the place the same way as they do on cry engine 2. But you'll notice for example in BF4 when you are in demanding moments or looking at a demanding view boost cuts out.
Windows 8.1 helps somewhat. But not that much with crysis. AMD cards don't have the problem but it's AMD, not my cup of tea they have their own share of problems/lack of features, but crysis will be fine.
And yes crysis still reigns as king.
Boost clock is bs trust me, it's just like how samsung phone's overclock when they detect benchmarks. :X /End rant of truth. I'm about a year behind in terms of everything but I doubt this has changed, there wasn't a fix for it at the time, let alone people who knew about this issue. You can reduce the stutter, I forget how, I think I disabled boost clock (might have been a bios mod) and took out any GPU overclocks I had and used a custom GPU utility to lock in a certain power mode (NVMonitor?). But they'll still be there, just less.