The reason for the high crit seems to be crit on most of the gear, plus boot enchant and the Molten Armor buff gives 3% crit as well. It is also more of a crit-stacking chardev for fire, that foregoes a little survivability.
improve freeze adds nothing and removes the best things frost has to offer.
about gear replace:
BoA chest w/ robe of power
Stoneweaver leggings w/ necromancer leggings
ring of demonic guile w/ underworld band
boots enchant should be fortitude