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We are as lost as you are to be honest, given that the 6 schools of magic as shown in the picture above have only been clearly separated about two years ago and not all of them have had enough development to this day. It would seem that life and death are indeed their own schools of magic as evidenced by druids and shamans as you say and seeing as the light and void come from their very own dimensions, so to say, I personally expect the same to be truth of the other sources of magic.
There seems to be a strong connection between the Arcane and Titans, seeing as arcane seems to litterally be the blood of titans. And just like there are the void lords, most of us speculate there being some sort of light lord, possibly the night elven goddess Elune.
I would bet that there are also "arcane lords, fel lords, nature lords and necromantic lords" of some sort that have yet to be even hinted at which could be developped in future expansion packs, but that is merely my fan speculation.