2. WW+CM + Frost Nova requires a certain number of crits within FN's duration. This isn't a linear function of crit chance (it's a Poisson Distribution, for the wiki-inclined)... so a 50% reduction in proc chance doesn't mean you need to double your crit rate to get back to where you were.
Oh the maths!...
Don't bring back bad memories from my bachelors studies!
Anyways, lesson learned: people exaggerate about the build not being viable anymore. You just need more crit. chance gear, that's all.