"Here are even more nitty gritty details, if you’re interested:

It can proc from

__any damage/healing event__. It keeps track of the last time it had a chance to proc for that enchant.

It calculates the difference in time since the

__last chance to proc__. It uses that time to determine the chance for that event to trigger a proc.

For example, if you have 22% Haste, it was 1.4sec since the

__last chance to proc__, and you’ve got Windsong, then the chance to proc is 2(ppm) * 1.22(haste) * 1.4(time since last chance) / 60 (sec per min) = 5.693%.

The ‘time since the

__last chance to proc__’ is capped at 10sec, so that your first attack of a fight isn’t a guaranteed proc."

source
im not sure about #1 here and i could really use some clarification... everything ive read about RPPM says that "TimeSinceLastChanceToProc" which is capped at 10seconds... 3 seconds into the fight my last chance to proc was like 1 second ago. so my 1st attack, and 1st attack only, would be 10x more likely to proc than my 2nd? or 3rd assuming 1sec since last chance to proc? and any subsequent attack throughout the course of the fight at 1sec since last chance to proc? but if my average time since last chance to proc (direct damage, living bomb dot, pyroblast dot, ignite dot, possible flamestrike/combustion dot) is like 0.5sec then on pull is 20x more likely to proc?