According to Blizz tidbits from the development, there are a couple key details to be aware of:
1.) KM can only proc on the main hand. That means 2h it's a non-issue, but for dual wielders your off-hand strikes don't matter as they cannot proc the effect.
2.) KM is capped at 5 ppm (procs per minute) for a full 5 stack. The RNG may give you wonky results on a smaller sample (read something under 1000), but on the grand scale that means regardless of weapon speed, allowing for sufficient hit chances, the speed of your weapon will not have an effect on how frequently you gain the buff, nor will your rotation. Presumably, though I haven't tested it, the talent gives you about 1 ppm per point on average.