People use Ice Shards talent to increase damage of Blizzard spell which they use to clear bunch of mobs on their way to boss. l am pointing out that this is actually talent that is not for boss fight but for out of boss fight or even out of dungeon/raid.
To prove that Ice Shards talent is useless l compared Blizzard with other AoE spell that does not use that talent, Flamestrike.
So as you can see on video, Flamestrike is better in terms of damage than Blizzard even with talent. We also saw that Blizzard is proccing more Clearcasting talent and thus keeping mana full at 100% at all time but Flamestrike is not lot behind so after 1:30 min test, l had 60% mana left.
Now when l started this test l was not fully prepared, l lacked Molten armor, Intellect buff even gems and enchants and ofc raid buffs and auras. But even with that we can see that those 40% damage difference cannot be dramatically change.
Thats why even on Arcane spec Flamestrike WINS and Blizzard remains only as PvP and leveling spell.
After l showed that Icy Shards talent is pointless, l will show why other option Frost Warding is good. Forget about armor increase l wont talk about that, l want to show its other value, and that is mana restore.
When you use Fire or Frost Ward, you get 30% chance to negate damage that you would take from enemies attack and instead get mana.
How much bosses are doing fire or frost damage?
Marro, LadyD, Gunship, VD, Sindragosa, Princes and LK so more than half ICC, should l count more?
Are you sure that will give me decent amount of mana?
Depend on boss but take a look on picture
Use Frost Warding talent to get to Icy Veins.