Just look to MoM in my opinion, a global mana pool and a tactical battle mana pool that drew from that, the further you are away from your capital, the more expensive spells are. This kept everything in line so that you couldn't become fully dependent on magic to deal with all battles (particularly those without wizards, which WoM has correct right now), magic was more of a support thing to allow you to turn the tides of battle a little. In tactical battle you only had a much smaller subset of magic you could use before you were depleted. Also casting spells wasn't always instantaneous in MoM, so summoning occurred over turns, and it again was based on a value of how much mana you could use per turn.

Honestly, while MoM wasn't perfect it was damn close, just look to it for guidance.

I think the magic system as it is now more accurately reflects magic itself. First of all, we're still using the old mana system (as opposed to the new one set to be implemented) and mana takes forever to regenerate, so each spell counts. Second of all, the dmaage output is now lsightly realistic! Since when did leather armor prevent a wearer from getting fried by a lightning bolt? Never. I like the magic system a lot now. Sucks for those people who have the glitch where magic misses all the time.