1:1 STR:DEX is the most balanced. Not the highest damage for any particular skill but not the worst either, just a good balanced stat allocation that will perform well.
2:1 STR:DEX favors you if you use skills that do around 900-1500 skill damage most of the time.
2:1 DEX:STR favors you if you use skills that do around 2k damage most of the time.
FULL STR favors you if you use skills that have low base damage but hit a lot of times (like multishot, level 1 oblique, etc.)
FULL DEX favors you if you use skills that have enourmous base damage (cannoneer skills, snipe from musketeer, etc.)
so really, just ask yourself what your bread and butter skill is, and optimize your STR:DEX ratio for that. If you don’t know or don’t particularly care, 1:1 STR:DEX is the most balanced build you can go with.
Source (my calculations):
http://imgur.com/eDlwbE1