Here are my observations and suggestions on game balance.
Every spell school has something to offer and is, in my opinion, viable for character builds. Due to much higher frequency of magic fountains than health fountains though, I think every character is really going to want either light or dark as a means of turning that mp into hp. I don't know whether or not drain is still useful at the end against the high damage monsters, but heal saved my life a hundred times over.
The balance for the edges could probably use a little bit more work though. Enhanced Power is the equivalent to one potion of gain energy, and Toughness is the equivalent to five potions of gain life.
Melee Training is really strong as it is, because it's the only way to deal damage that costs no mp. In other words, any character that does not have that edge is helpless if they find themselves if they run out of energy. I personally think that it's really nice to have that to fall back on, or even as a primary means of attack.
Staff Bolts on the other hand, seem like they could use some work. Their damage at the beginning is very nice, but keeping it up to par with the enemies in the dungeon will require a massive investment in its edges, and since each rank in Powerful Bolt only increases it by 1, it will likely still be left behind by other forms of attack in the end.
Compare staff bolts to the elemental Lightning Bolt spell. Lightning does more damage initially (at least I'm pretty sure it does...) and can be learned on the first level with the first orb. Once they become available, you can take the Elemental Attunement and Elemental Mastery edges to gain +5 damage in only two edges. To get the same increase with staff bolts you would need to use 5 of them, which is more than half of how many you should expect to get in the game. Lightning bolts are also perfectly accurate without the need for any additional edges. Staff bolts can still miss even after taking the Accurate Bolt edge. Lightning bolts can also pierce through lines of enemies, hitting multiple targets in one shot. To obtain this ability, a staff bolt user would be required to take the shaped bolt edge as well. Finally, lightning bolts have a chance of inflicting paralysis, which staff bolts cannot permanently gain.
Short version: I consider the lightning spell to be a viable weapon after taking only two edges. For staff bolts, the player must take *at least* 7 edges (enhanced power x 5, shaped bolt, accurate bolt) to get to what I would consider a comparable form of attack.
Considering that lightning bolt only costs 1 mp more than a staff bolt, I think staff bolts come out looking pretty bad by comparison.
I don't know if Alchemy Training is worth taking. Fast preparation of the potion you need is useful, sure, but I don't think it's worth the valuable edge point, and a good player should be able to plan ahead well enough most of the time to get by without it. I'm not sure about Advanced Alchemy though; being able to produce whatever potion is best for the situation instantly would definitely open up tactical options for the player.
As for the other edges, Charge Control is nifty, but with staff bolts being as weak as they are late game, it doesn't seem worth bothering there. Charged melee attacks are good, but I would place more value on simply taking another rank of melee training all things considered. Finally, Contingency is very nice, and I strongly recommend taking it once or twice after you've made it more than halfway through the dungeon (taking it at the start is kind of wasteful, in my opinion).
Lastly, I have not tested the spell school edges, but they generally seem good. Guessing based on the descriptions, and it is only a guess, so naturally take this with a grain of salt, I would say that the Dark edges seem the weakest, and depending on how Alien Mentality and Physiology work, those two could well be overpowered.
So here are my recommendations:
Staff bolts are good at the start of the game, but require way too big of an investment to be good at the end. Perhaps lowering the base damage by one or two and then increasing the bonus of Powerful Bolt to +2 would be in order? I definitely think that either the base accuracy of staff bolts or the bonus from Accurate Bolt should be increased as well. It may be worth considering giving staff bolts 100% accuracy, and just take the RNG out of the question altogether.
If Melee Training seems too strong right now, it might be good to lower the bonus to +1. This would be really terrible for melee attacks as they are now, so it may be good to add +2 or so to the base damage of melee attacks. This could also make the early game too easy though. It's kind of a tough problem. As a last resort, I suppose you could give them a chance to miss as well as an "Accurate Strike" edge (or something like that) to take an edge point or two away from melee fighters, but I really like the dependability of melee attacks personally.
Enhanced Power needs a huge boost. I mean a really gigantic boost. At least to +5, or even up to +10 would not be unreasonable, I think. To be the equal of Toughness as far as levelling and stat gain potions are concerned, it would need to be +15, and I don't feel that Toughness is overpowered.
Charge Control is not a bad edge, but I think more could be done with it. If staff bolts were improved, that would probably be enough by itself to make it valuable.
Here's an alternate idea though: what if charged shots could become the perk that make staff bolts worth using in the first place? What if there were an edge that caused the charge level to go down by 1 every time the player takes a step instead of depleting completely? This would allow the tactic of charging up a shot to 3, and then ambushing an enemy around a corner with a level 2 attack, which would be good for those blasted summoners, and other annoying enemies.
Another idea would be to add new edges that open up after taking Charge Control like Advanced Alchemy currently does. A "Quick Charge" edge that makes charging faster/instantaneous like the alchemy edges do would be helpful, and a "Free Charge" edge that would take away the mp cost of charging, but would still make them take a turn could be good also (though obviously both of these together is not a good idea).
Anyway, that's everything I can think of. I tend to be pretty verbose, so sorry for the gigantic size of this.