http://simulationcraft.org/510/Raid_T14H.html from live.
How we got onto envenom damage I'm not sure, because Soxy's post doesn't mention it, but let's start from that profile. Assume the 20% buff is a 20% buff, and, before better gear, envenom's average hit should be around 144k in BiS, with crits averaging 238k.
POISONS! To get back to what Soxy was trying to discuss. I'm fairly certain that was an attempt to pull random numbers out for the sake of good napkin math, because 100 is a nice round number for multiplying - and showing that given a severe mastery boost, the crit loss is not just countered but overpowered by the increase in damage of non-crits and the fewer remaining crits. Introducing current values from SimC: Deadly proc non-crit 17k, deadly proc crit 37k (odd discrepancy but I'm not about to look into it - Skull Banner?) at 7665 mastery (from gear - we gain 17.5% poison damage from buffs/base if I'm following this accurately). That's 90.23% gain; with an average instant damage of 23.7k, DP instants hit for approximately 12,458 before mastery. RoR in that profile would proc for 13,444 mastery. Account for only crit from agility, buff the average instant damage with the lower crit rate by the new mastery value, and you have your damage listing per hit on average.
Toss haste in there afterwards...
I still think the easier way to do a hackneyed model of this is to sim yourself normally, and sim yourself with 0 crit rating, 0 haste rating, and 2x(normal haste/crit) added to mastery artificially by manipulating stats in SimC's profile.