Confused on critical hits and sustained abilities...

currently playing a rogue. i have dual striking, but don't know if i should use it because the the talent says that "the character cannot inflict regular critical hits or backstabs". does that affect riposte, cripple, punisher,etc. or just my standard basic attack?

i'm having trouble deciding if sustained talents should be used all the time or just during tough encounters. can someone clarify and maybe toss a tip or two my way? i'd appreciate it! thanks