Frostbite and Shatter are staples in the frost tree, imo. And even though they buffed Wand Specialization, I still don't see it as worthy of my precious talent points in the Arcane tree. But that's just my opinion. Some people think Magic Absorption is worthless, but I love it. And Permafrost is more for pvp, imo.
If you're going to go that deep in the fire tree to prevent you from getting PoM, then you can skip out on some of that other stuff in the Arcane tree, too, like Arcane Impact.
Again, Frostbite and Shatter. You don't need to max them out, but you'll love everytime your frostbolt freezes the target in place so you can slow them down even more or use an extra Ice Lance (which would have a higher chance to crit from Shatter).
You don't need Frost Channeling for pvp, that's a pve talent - it reduces mana cost and threat. Put those points in Permafrost. A lot of mages go fire or frost for pvp. Fire mages love Dragon's Breath and Blazing Speed for pvp and frost mages love the water elemental for some extra dps and the extra frost nova.
That's just my 2c. I don't claim to be the know-all, be-all mage. :P
"You'd be surprised how many people violate this simple principle every day of their lives and try to fit square pegs into round holes, ignoring the clear reality that Things Are As They Are." -Benjamin Hoff, The Tao of Pooh