The biggest flaw in this build is that he took Markovian's Advantage and Zolhan's Technique from the Soldier tree and Amarasta's Quick Cut, Whirling Death and Execution from the Nightblade tree. This is an incredible waste of DPS. Execution is the star of the show, yet he's muddling his chances for it to proc by taking a heap of other skills that can proc. Certainly they are all good, but they can't proc at the same time. I'd cut down on the passive procs.
How exactly is he cutting down on proc chance? He has only 66% of the autoattacks covered in the no-gear build and 100% with gear.
Looking at the build you made, you clearly didn't understand how those procs work. They cannot proc at the same time, but they override auto-attacks. In the build you modified 20% Zolhan, 20% Execution: game rolls 0-99 for each auto-attack, 0->19 is zolhan, 20-39 is execution, 40-99 is auto-attack. If you add another 20% proc chance it will take the 40-59 "bracket", not cut into execution.
You diminish proc rate of execution only if you go over 100%, when it becomes 2000/total.
Also, if you go Cadence, Belgothian's Shear and Amarasta's Quick Cuts produce 2 and 3 hits which count towards cadence and if cadence triggers during those procs, it doesn't override them.
But don't mind me I'm just a TQ hater amazed by the pure genius behind these clear mechanics.