I dont think the pestilence change will affect frost aoe that much tbh, we still got dnd/HB and the new BB. With your spec you are giving up 900ap from bladed armor plus 10% overal damage and 5 expertice from thundra stalker just to get ub. Your aoe dmg/threat might go up a bit but your single target threat would go down alot.
Erm just realised you didnt have bladed armor in your current build
Still 10% overall damage and 5 expertice is hard to replace.