Nostalrius Begins - Quality wow vanilla realm (1.12)

How is the proc of arcane concentration on blizzard like? Talent says that it's on every spell damage hit, i remmember that on feenix it could proc of every blizzard thick, so i could finish mob packs with full mana, however on my local server it does not proc at all and here on nostalrius i have exactly no clue how does it work.
So i'm here asking ya if it's worth to go at level 37+ with some points into arcane three or go stright for frost barrier?

It can only proc on spell cast, so once. That being said I recently leveled a mage pure arcane and it was a blast so take that as you will.

Aye, I already tried that and realized that it was a bit huge mistake that extended my mount purchase for awhille. Also, it seems like that it takes blizzard as one spell hit and completly ignores amount of your targets (it does not even proc as often as it should be, if you were blizzarding only target).
Quick example, today i was continuously farming murloc camp in dustwallow marsh for over 30 minutes (i think it was something about 18 pulls of 6-8 mobs). About 20% of all my novas/cocs/arcane explosions gave me clearcasting, but i did not get even one single proc of blizzard (using 3-4 blizzards on each pull, depends on positionin of mobs when they run away).

If anyone ever was wondering about using blizzard with arcane concentration for leveling, DO NOT DO THAT .

With leveling don't mess around, just go full frost and thank yourself later.