According to some early theorycrafting our calculated stat priority list is:
Accuracy, up until ~216
Surge, up until ~200
Crit, up until ~300
Cunning
Crit, up until ~400
Surge, up until ~250
Power
Crit, beyond 400
Surge, beyond 250
Accuracy, beyond 216
There's a gunslinger/sniper compendium at http://sithwarrior.com/forums/Thread-Marksman-Sniper-Compendium