I had heard that the 3.5 game is more balanced if you have the "fab 4" of Fighter, Rogue, Cleric and Wizard, but the Wizard is restricted to blasting spells (and say read magic) and the cleric is restricted to healing spells (including also things like remove paralysis, neutralize poison, raise dead, restoration, etc.).
Has anyone tried this? Would that make the game more balanced?
The problem here is that there are certain spells that overshow the other classes, and that (at properly high level) casters have enough slots to memorize them and still do their original job.
To whit: Invisibility, Knock, and Spider Climb are better than Hide, Open Lock, or Climb checks. If the spells granted the wizard free use of the skill with a bonus (on par with maxing out the skill, for example) they'd be equal. As they are, they're superior enough that, unless your game requires constant multiple uses of those skills, the spells are more than enough to suffice its use and limit's the rogue's ability to really shine.
Similiarly, a cleric's buffs are supposed to make everyone better (boosting AC, restoring hp, adding to attacks) but are best spent making the cleric the focus and uber-focusing him to be better at fighting than a similarly buffed fighter. (Divine Power, Divine Favor, Magic Vestment, Gtr Mgc Weapon). Ergo, the cleric can fight on par with a fighter AND still heal and flamestrike foes. (Wizards can pull a version of this too using tenser's transformation and polymorphs, but cleric's get the bene of great weapons, armor, and hp even when not tweaked out).
This doesn't EVEN begin to cover the problems with summoned monsters, wands and other cheap X use magic items (to avoid the need to waste spell slots on these spells) and broken metamagic and divine feats which further augment to the caster arsenal.
Its really easy to fix a lot of this. Pathfinder went that way in a lot of ways (nerfing spells primarily) but fixing wizards so that they're magic isn't a "I win" button, fixing cleric buffs to be better served as aid to others (a +1 to all allies is better than a +5 to one ally) and the removal of cheap magic item creation and broken metamagic/divine feats goes a LONG way to fixing the problem.
So you don't need to limit clerics and wizards to just nukes/heals, but you need to make utility magic and buffs stop stealing the show.