To the OP--
Your build isn't bad, there's two changes I'd recommend. Firstly:
IMO, Magic Absorption is absolutely useless for raiding. You're not going to be taking many hits, so the 10 resistance is useless, and since you're not taking many hits, the resist mana refund is wasted too. I'd take those 5 points and put two into Wand Specialisation, and 3 into Arcane Impact.
A lot of people will say Wand Spec is a waste, and in most cases I'd agree (I don't have it, but that's because I'm a PVP frostie
) but in this case it might get some occasional use when you go OOM, anything at all is better than Magic Absorption which is pretty useless for raiding. And Arcane Impact is always nice to have too.
I'd keep Improved Counterspell too btw, it's not just nice for PVP but is useful for PVE too - not so much raids, but in 5 mans etc. it can come in handy.
The second thing:
I'd ditch Blastwave and get Slow. I used to be a Arc/Fire mage when I raided (switched to frost for PVP now) and I found slow quite useful against some bosses. It's a spell that a lot of people overlook, but I found when running dungeons with people who were aware of how useful it is, they'd often be asking me to drop it on bosses to slow them down. This is maybe not so useful in 25 mans as it is in 5 man dungeons or maybe 10 man raids, but it's still better than Blastwave, which IMO is pretty useless for anyhting other than PVP on the whole. On the odd occasion that you do need to AOE, you can just use your arcane explosion.
But, maybe you have Blastwave for PVP, or just because you like it, I dunno. Just some suggestions
