Anothere Talent Build QuestionFollow

Since hitting 70 I have kept doing BG's and I've noticed i'm getting silenced a lot. This is an awsome talent. I love to do BG, and my guild is going to start doing arenas, but we will still need to raid to get the keys and such to for the instances with great gear. I'm thinking seriously of changing my beloved frost heavy build. I really like the 100% chance to silence the 2 points in improved counterspell will give me, but I'm having a hard time deciding what talents to give up on my frost tree to get the neccessary point in arcane. My current build is:

http://www.wowarmory.com/character-sheet.xml?r=Quel%27dorei&n=Varilhigh

I'm thinking of going to:

http://www.wowhead.com/?talent=of0E00bZZVAMfof0sbqt

What do you guys think?

IMP CS is definitely better than WC. I would totally take a guaranteed silence on a healer/etc over a slightly higher chance to crit after you keep applying frost spells.

tough choice. I would probably go permafrost so that if you see a flag carrier or something you can rank1 frostbolt them or better and it will really slow them down. Frostbite is nice, but if it doesn't proc it was useless.