[Executor]

I'm not sure there can be balance among magic schools in the real sense as some tend to be more battlefield oriented like fire evocation, and others tend to be more summons oriented like blood, which is hard to use on the battlefield due to slaves being able to get killed and being needed for every spell, and all the spells fatiguing the casters too fast, etc...
But that doesn't necessarily put one magic school over another, as all of them have some up and down sides, which is a seance balances them out.

So, it's my opinion that magic schools are balanced, more or less, and one can make due with limited diversification.