Frost seems like the default choice. Slows along with other tool kits would be a safe pick.
For fire, I like Fire’s causterize effect. Frenetic speed seems good too. Dragon breath’s effect could be another tool for mass disorient for packs.
For arcane, I’m not really familiar. I guess burn down fast? Drink, repeat?
Would be cool if they made the leggo chest ability baseline for all specs or part of shimmer talent.