Simcraft is simply totally wrong. Practice showed a totally different picture, especially because of high mobility, utility, very strong cleave and far overpowered scaling.
Look at Raidbots 25m and 10m:
http://raidbots.com/dpsbot/Overall_D...default/#5fvjj
http://raidbots.com/dpsbot/Overall_D...default/#5fvjj
Fire mages were on average already 20% ahead of elemental shamans and balance druids. With time cming, it would have gone up to 30% or even more in T16 heroic.
What we still have to see: it's very much possible that arcane is still overpowered or even frost. So fire will still be best specc for some fights, overall ebaten only be combat rogues - but with a huge distance to the other damage dealers.
And simcraft simply is and stays wrong, like it always was.