The Magic system should be a lot like Magic the Gathering (as in fact Brad himself said at PAX while next to the WotC booth). Each Magic type is the source of the damage, not the damage type itself.

The question is what should those damage types be? There is no need to tie it to the "mana" types and I think that would be awfully limiting and constrained.

I think the original damage types are excellent. I would just want to see poison/disease/bio/corrosion added as others mentioned.

Also, I see a lot of posters assuming that protection of one type would offer no protection against other types. Why do you assume that? It isn't that way in Galciv and I don't think it should be that way in EWOM.

Fire protection 6 for instance might automatically give you 4 ranks of lightning protection (you don't burn after all), 2 ranks of protection against Freezing (effect of insulation) and 0 against Mystical. Rank 6 Freezing protection might offer an entirely different slider (4 against Mystical, 2 against lightning, none against fire), etc.

I like that you can modify physical attacks to other types - without that, there'd be a real problem with traditional troops having a single damage type (mundane).  There's a similar issue with PnP D&D - you can pump armor class pretty easily, which means in a caster/fighter showdown, a caster can boost defensive capabilities and shrug off any physical attack easily, but a fighter has to boost multiple types of saving throws; that's one of the more subtle but sweeping balance challenges.   

Yeah why not break up mundane damage more, into counters?

E.g. melee vs. missile

blunt damage vs. piercing damage

Cavalry shock vs. Infantry vs. siege vs. super-sized tooth and claw.

Sharp pointy sticks vs. cavalry

Also, only four spheres of magic is pretty stereotypical and probably boring. Even MoM through in law/chaos, and life/death on top of those.  D20 expands on that a bit more.  Maybe go back to the drawing board and envision a detailed, RPG-like magic system.