Hey, I don't know if something has changed, but I tried following this guide and found that Frost is absolutely -not- the go-to spec until like level 40. They don't even get all of their procs until like level 37, which causes them to be extremely underpowered until they reach that level. Fire also has similar issues, but not to the same degree. This is based on leveling with unenchanted heirlooms, but I found arcane was -far and away- the absolute best specialization until you hit around level 40 and fire and frost end up catching up to it.