22 Fire/29Frost is Gnimish's current build. I get very effective damage vs. large groups, Flamestrike, Frost Nova, Blastwave, Arc Explosion 1-2 times, redo Frost Nova(Reduced Cool Down) and FireBall or FrostBolt the remaining. Its an excellent grind or PvP build.
Also is very effective in Instances. I ran UBRS yesterday, was 2nd in overall damage, I aggroed very little, and if I did I threw up Ice Block, others get aggro back and I can pound away again.
I only have about +140 damage or if I use my Fire Ruby, I gain an extra 100 damage on 1 Fire spell which I typically save & use with Blastwave.
I crit regularly with all my spells, Flamestrike & Blastwave give me multi crits usually in a single cast doing 1000 damage crits. My Fireball and Frostbolts crit around 1100-1200 regularly.
The only downside is if I don't crit regularly my damage is a bit low versus other more standard builds. Overall though I'm satisfied with it.