MSW change is a def. nerf from its original form 2 builds ago.
prior to first nerf it took about 10 seconds
the last nerf made it so it if you are unlucky you could never have a full stack
now this 'nerf' made it so you will have a stack every X minutes based on the PPM. (so if its 4ppm then it will proc approx every 15 seconds, then 5x15 = 75s)