The simulation ran over the course of 360 seconds (6 minutes), with a base crit rate of 15% (~500 crit), and assumed IR usage.

100000 trials were run, and here are the results:

Trials: 100000 Procs: 6034321 BLs: 6556674
So if I'm interpreting correctly, your 15% crit rate simulation resulted in 360 * 100,000 / (6556674) = 0.1821 bloodletters per second.

The assumed uptime for both WB and VB is 100%? And the simulation is based on 2 chances to crit simultaneously every 3s? 100% Straight Shot uptime for 10% more crit?