The problem with what we have now is the requirement to sim everything.
At least with socketed gear and reforging, you could buy some gems from the AH and beat on a dummy to test out your mad-genius idea.
Now it’s too expensive and time consuming to collect all the different pieces of gear you need to test anything. What if I stack haste? What if I stack crit? How will my rotation feel if I go against all the meta guides and try this combination instead?
Gear customization should be the end game - not random effects and procs.