We miss somthing for faster casting - apply spells - mele with Agility medalion can easy interupt and hit chaneling spell Frost Wich - to easy for me and no caster medalion with usfull improvement, Agility for me is useless (or I am wrong?)
After interupt FW cant start casting again I can only run away if lucky

attack speed buffs (like medalion or paladin aura) actually increase any animation spped -- regular attack animation or power attack or casting abilities
not sure for 100% it will increase stacks rate for winter cold, but that seems to be logically correct as for me

One even drink potion faster:)