Alright guys I'm gonna jump in headfirst like I always do! You guys are throwing around some big ideas and whatnot, but I'm just gonna say my piece.
First: My Cred. I've won twice. Only Twice. Both times were with a spell caster. First one was a Wizard, second one was a Necromancer. Both spellcasters. The Wizard closed the gate, the Necromancer killed Andor Drakon and became an evil god.
BUT: Once they hit that last level, I think 95% of my spells were cast directly from hp. I'm not even joking. I'm almost positive Andor Drakon drains PP. And on the last level, both of them had to deal with teleporting Balors and had to get away from both them and Fistanarius, and neither one was too big on getting hit by Chaos Creeps.
Also, the mana temple. Had to HP cost from there, and nearly died both times anyways cause the boss there is no slouch.
Now, my wizard, she was a fragile thing, who pretty much casted her way through the game. She probably could have tried melee some more. But my Necro, she barehanded almost every monster in the game (for shadow touch), and pretty much the only thing I didn't kill that way was some really tough Golems, and the Balors. She could kill Chaos guys with her barehands, and the golems with her flail.
BUT EVEN WITH ALL THAT: She still casted a lot. Especially against those Balors and in the Mana temple and against Andor Drakon.
Was it easy to keep casting? Yes. Was it easy to heal? Not as easy, but it wasn't super huge. She had cure serious wounds, which I used a lot of.
But the point is, she HAD TO. I didn't have any PP! It's not like I could wait around for it to regenerate! Both chars were that way. I had a few blessed scrolls of power, which I read, but honestly it was kinda pointless cause they didn't recharge me enough for it to matter much.
So what am I getting at? I don't know. But I'll say this. At the end, I didn't have a choice. It was cast from HP, or not cast at all.