Might also add that if you play with war mode on, you get deep shatter, which makes your frostbolts really strong (stronger than ice lances, and you can hit a frostbolt together with an ice lance on a frozen target) - and between frost nova, your elemental's freeze, ice nova, frostbite and brain freeze procs, you're doing that pretty much constantly. I don't think the other specs gain nearly as much consistent damage from PvP talents, or just the fact that enemies can be frozen in general.