Your situation fits case #3 here (
Rogue DPS Simulation Spreadsheet). It's still on previous page.
About mongoose and crit cap, I did not include it there on purpose. I suppose you can add both mongooses up if you want to see the worst case scenario. However, the more procs you add to that, the less likely it is to see that scenario. Right now it's simply showing the trinket procs, so you know if some of your procs are wasted. Adding double mongoose to the crit cap indicator will probably make the cap number less informative if not misleading. Consider what happens if you have DCG, DC and double mongoose. Right now the indicator shows only the two trinket procs, so the uptime of that is probably around 15% (an educated guess). If you add double mongoose proc, which is independent of the trinket procs and has an uptime of about 30% for mutilate, then you will likely see a red flag that you are going over the crit cap, but you should know that you are only going over the crit cap during about 5% of the fight.
So I will think how to present the crit cap information better. Perhaps I can show several crit caps with and without the mongoose procs.