No need to calculate. Just get 2 basher, theads and midas or hyperstone. The % bash will give in perhit so the faster you are the greater % bash can struck. Think like this.

In 1 seconds

1 hit is 85% + 15% bash
1 hit is 85% + 15% non-bash
1 hit is 85% + 15% bash
1 hit is 85% + 15% non-bash

Faster you are the chart run like this in 0.1 sec
So you get perma-stun.