Clear casting vs icy veinsFollow

The best way to compare two abilities usually involves a spreadsheet and number crunching, but I think in the case of these two abilities that may not be necessary. The clearcasting ability is extremely valuable in raids, as you get a consistent proc on an ability related to one's mana consistency. This can often be used to cast your more expensive spells, and many mages do not hesitate to essentially waste their first 5 points in arcane to get this. So as far as mana consistency in a prolonged fight is concerned, I think this ability is second to none for a mage. The problem, however, is that mages now have numerous ways to keep their mana up during a fight as of the last few patches. With the improved evocation, mana gems (3 charges), and intelligent potion usage, fire mages rarely run out of mana during raids. This being the case, I would probably favor Icy Veins due to the increase in DPS it provides. In the case of PvP, I would always choose Icy Veins since shortened casting time is far more useful than somewhat improved mana consistency in these situations.

Very different talents, as I'm sure you're aware.

PvE
One sacrifices mana efficiency to get higher dps in shorter fights (Icy Veins). The other increases mana efficiency for greater dps over a long fight (clearcasting).

PvP
Icy Veins > Clearcasting. Faster casting and more snares. Sweetness.

I really don't think mana is much of an issue prior to and including most of Kara. My raiding experience is minimal, so I can't speak to anything beyond that.

I would assume so, as long as you have it activated



If you have the mana and are good at keeping yourself from being oom, then Icy Veins is the way to go. It is a decent increase in DPS for the sacrifice of sometimes getting a free cast.