2 things.
First, I have 56.5% CHC without my helm and cant roll both CHC and Impale %, so in this case shouldn't I just go for impale %? I mean, after 50% arent you just increasing the probability that 2 hits will be consecutively critical? (In my case that would occur once every 20 hits: 50% means once every other hit ~5% means 1 in 20 ergo every 20 hits will create 2 consecutive crits)
Second, how does pain enhancer really benefit this build? I just try to kill a boss, elite pack, and move on to the next. I make it my business not to waste my time hitting trash. Wouldn't strick