Wanted to try something different.
Possibly better mana management
No Living Bomb
No Piercing ice
No Icy veins
The major headache is the missed-out burnout. 50% more bonuscritdmg in a critdependant build is not wise to leave out. BUT consider this: 50% more damage on crits, plus the 100% from Ice shards translates into a 2,25 crit multiplier (a spell that normaly hits 100 crits 225). Without burnout it's only 200, meaning Burnout gives about 12.5% extra damage when you crit. ttw gives 12% constantly.
Focus Magic gives 6% (if you find another mage with this spec) increased crit, vs 6% increased damage from piercing ice.
Then you also lose living bomb and Icy veins for Clearcasting