Hello, this is my first time posting on a forum, ever, but I would like to put my two cents in, as it were, even though the game probably is to late in the development process. So even if my post would be read and considered applicable, it will probably not have any effect whatsoever. Well, one lives in hope I guess.
Ok, now to the actual proposition: How come wizards are limited by spells per day?
I've always found this higly confounding, and that it messed with the balance of the game. It seemed uneeven, since I could clear a dungeon with a fighter (with careful playing and attention to details), but with a wizard I had to rest every five minutes because he needed to cast a particular spell and/or had run out of them. Even when in BG 2, where you could make superior wizard/fighter multi-dual classes, somehow the wizards abilities seemed to lose to the convenience of just hacking and slashing. Although, it was fun to fling fireballs, and such, the more superior option was all to often to just enhance your melee ability, or you would have to rest every five minutes anyway to cast that particular spell. The game designers tried to remedy this with the use of wands, and other limited use items, but it never really seemed like a viable option, unless you cheated a bit and exploited someother flaw in the game mechanics, such as bying and selling wands to recharge them (which would not have been monetary possible without thieving).
If spells per day is supposed to represent mental fatigue, then shouldn't fighters get tired as well and have a limited use of slashes? Surely it must get tiring wielding that blade around all the time? If you then have limited resting, as I understand PoE will have, then spells/day is even more odd and artificial, and will make wizard even more difficult to use.
My proposed solution would be to have spells per day tied to stamina, a derived statistic from constitution and resolve, and not to level only. In fact why not have a general effectiveness rating tied to fatigue? A sleep deprived character can't fling as many spells as accuratly as a well rested one, nor can a fighter swing his sword as well when suffering from muscle strain etc.