I will admit, the white dragon cloak is a genius kinda move for an adversary that everyone and their mother (with any kinda magic to bare) will be throwing cold/ice spells at.
Genius? Only in the sense that me wearing a coat out when it's cold makes me a genius! Seems like basic common sense to me. The question is why, up till now, they've all been so intensely stupid as to not do something like that?