Made an account just to chime in..
I've had the same problem for over a year now, and no matter what I do - nothing seems to fix it. Interestingly enough, my hardware is almost identical to yours.. (i7 4790k, GTX 970..)
Tried everything mentioned in this thread and beyond, NOTHING will remove the microstutter. I've even clean installed Windows several times since the beginning of me experiencing this bug.. it still persists. In my case, the FPS indicator doesn't actually drop when I stutter - nothing I can see seems to acknowledge it. Does your FPS *actually* drop in relation to the stutters? We might not being experiencing the same thing if you do drop FPS, but the similarities in our hardware suggests a connection..
A lot of threads I've read theorize that Windows 10 is the problem; though this does not seem to be your case. To test this theory for myself I dual booted into Ubuntu, installed Warband, and fired it up. Aside from some bugs caused by not having all of the dependencies Warband uses for Linux, the gameplay was silky smooth. Very strange indeed, as this seems to suggest it is not the hardware that is at fault. No other game stutters like Warband. After playing Mount&Blade for nearly 6 years now, this stuttering is really making it hard to play.