Though mastery increases the sheer burst of an attack, crit only increases the CHANCE of more burst of an attack.
If a CS hits for 50.000 damage with 75% mastery and 20% crit, one would hit for 50.000+10.000 (on average). 60.000 x 1.75 = 105000 Damage.
Seeing as how mastery requires over half the rating for a % as crit,
If a CS hits for 50.000 damage with 35% mastery and 40% crit, one would hit for 50.000+20.000 (on average). 70.000 x 1.35 = 94500 Damage.
In overall dps, mastery outweighs crit.
Now for a burst situation. If I were to hit a 100k TV with 80% mastery and 25% crit (10% from INQ). It would hit for 180k normal, or in case of a crit. 200k x 1.80 = 360000
With 40% mastery and 40% crit (10% from INQ). A normal hit would do 140k normal, or in case of a crit. 200k x 1.40 = 280000
Conclusion, if you want a higher chance at a good burst, stack crit. If you want a consistent high burst, stack mastery.
Including haste would make this a very difficult decision though, personally I stack STR > Mastery > Haste > Crit, and this works out great for me