My math there was fairly accurate, although I should have used a lower value for crit's SEP. Crit tends to be less valuable when used as a proc. Simcraft was just updated today (Not officially, you have to compile it yourself.) to include the trinkets. I ran a bunch of tests and the results were almost what I predicted, just engineering threw a wrench in it.
(I can't post links yet, but the following is in the Fury Of Pandaria thread.)
IF YOU ARE AN ENGINEER AND SMF:
Darkmoon Card > 5.1 Trinket. by a significant margin, 400+ dps increase in most cases.
Also, super-important here: If you DO use this trinket as an engineer, use bloodbath with your springs, NOT the trinket. Use the trinket on your next colossus smash. Trinket procs/uses have always been an area where comparing SEP values is difficult, as the value of crit isn't quite as high when you only consider a 12 second window.
IF YOU ARE NOT AN ENGINEER:
<490 Ilevel: Darkmoon Card > 5.1 trinket
490-500 Ilevel: Darkmoon Card = 5.1 Trinket.
>500 Ilevel or Titans Grip: 5.1 Trinket > Darkmoon Card.
Ilevel's are educated guesses by myself after running a couple of different gear-sets through. They have an error range of + or - 4 ilevels, sim your character to find out for sure.
Updated trinket results again.
My results for SMF:
BEST:
Heroic Lei Shen's Orders
Regular Lei Shen's Orders
5.1 Trinket (500+ Ilevel and NOT Engineer)
Relic of Xuen
5.1 Trinket (<500 ilevel or Engineer)
Carbonite Carbuncle
LFR Lei Shen's Orders
WORST:
AWFUL: Coaster
TG:
BEST:
Heroic Lei Shen's Orders
5.1 Trinket (Skullrender)
Carbonite Carbuncle (Only if crits SEP is above 1.2, roughly 505+ ilevel)
Regular Lei Shen's Orders
Relic of Xuen
Carbonite Carbuncle
Chorium's Coaster
LFR Lei Shen's Orders
WORST: