My main concern is if frost is viable in comparison to arcane due to how often shatter crits proc. Im not sure if we can acheive the necessary crit to have it occur regulary. If not it would make sense to go arcane in all situations.
I'll rephrase this so I can work with it:
IF X does not do as much damage as Y, then Y should always be used.
BECAUSE X can only do more damage with Z it isn't "viable".
Answer 1:Lets assume frost doesn't do as much damage. So what? Now frost isn't viable?
- Frost still has instant CoC AoE root, which immediately removes melee from fc/healer/self/other
- Frost still has ranged AoE root which immediately removes melee from fc/healer/self/other
- Ranged AoE root can be cast while silenced/sapped/interrupted, may require good pet control vs prot pally
- Ranged AoE root can be cast 100+yds away with good pet control, you can keep an approaching hunter/x from even joining the fight till its too late
The big thing that ppl miss with the root is that is saves time and mana. It allows: the team to put more dps on target; healers free globals to dps, cast slow heals, or to move; a way to stop enemies from making a flag pass; dps time to bandage or get healed.
Answer 2:Lets assume frost does as much or more damage. So what? Now arcane isn't viable?
- Arcane still has a blanket silence which can stop any enemy instant casts or get the opening shots on another caster
- Arcane can still do a large portion of their damage while moving
Movement is incredibly important in a los environment. This allows you to: make up for mistakes in reading opponents; close the gap on runners while damaging them; hover inside hunter melee zone (till MoP at least); move from behind los and get a "free" hit in; position yourself for a nova.
Answer 3:Lets assume all the specs do about the same amount of damage. So what? Now fire isn't viable?
- Fire still has impact, which allows kills on targets that are otherwise very difficult to kill
- Fire is the only spec that gives a secondary interrupt with impact
- Fire is the only spec that can apply a dot to keep rogues from maintaining stealth
- Fire is the only spec that can apply a ranged aoe dot with pyro+impact
Pyro + impact is the most unique combo in this bracket. If you keep a pyro rolling for impact procs you can ensure that any stealth in the area will be forced out of stealth. You can save impact for key moments on secondary/tertiary healers or for times when you need to stop a flag pass.
Summary
If you can't read opponents you "should" be playing arcane. How will you know this? If you start a cast and it doesn't land because of los or out of range, you are doing it wrong and "shouldn't" be playing fire/frost.