Originally Posted by
Schizoide
Fallen Crusader is 2 PPM. The formula is
(swing speed)/(60/PPM)
So if your 2H weapon has a 3.6s base swing speed it has a 12% chance to proc on every hit. Melee attack speed buffs like Icy Talons, Unholy Aura, Bloodlust, etc, do not impact the base swing speed, so they will give additional procs.
Uptime is approx 75/90/80% for DW frost, 2H frost, and Unholy respectively. That assumes DW only has FC on the offhand, of course, if it's on both hands uptime will be higher (but total damage, lower.)