I play frost since level 1 on my toon, not because it's necessarily the best but because I like it, so I would not want to switch spec just to achieve proving grounds, especially since I intend to play the further heroics in frost anyway.
I have switched Mirror Image for Incanter's Flow. And I do use the Alter Time to help me switch places on high movement.
I will check the Ice Nova as you propose, thank you.
I do also use the Water Jet from my water elemental when my Frozen Orb is on cooldown to help proc the Finger of Frost.
Thank you all for your help, and keep sending me yo