Wankstein

This is false. Lower ranked frost novas do not 'take more damage' to break. Also, it is not damage based, it is chance based. Sometimes you can hit a critical hit without breaking the nova, and other times you can break it with a normal hit. Since different ranked frost novas use the same freeze effect, the chance of breaking the nova is the same regardless of the rank. This means, for highest mana efficiency, it is wisest to use rank 1 frost nova.