Criticals are okay. Sure there are some crit builds but they're not optimal. It's just that if you're starting it is not recommended to PvP with a class like Sinx, which needs tons of gear (well, maybe not TONS, just a decent set.) Not to mention Sinx + Double Attack = really powerful. It will still be hard for you to use criticals to fight mainly as:
1) it relies on some luck which will sap your other stats
2) the best critical rate comes from a Katar, which means no shield usage
3) it's hard to get high crit rate from dual wielding daggers
I cant think straight lmao.