Hmm.
Just an idea: If you don`t want the rogue to be sneak attacking, and don`t like the bard casting spells, why not just strip the sneak attack and add Bardic Music & Knowledge? Perhaps it will still need some tweaking, but it might work...
D&D 3.Edition was designed (at least in its core, I don`t talk about some splat books and so on) to balance all classes against each other, so that no one will ever outshine someone, especially in combat. Combat does have much to do with the statistics, but Roleplaying a "social encounter" does also need some "actor" talents, and it also takes much fun if you make it only by rolling dies... (You can use the game mechanics to decide difficult situations ...)
So, the designers focused on battle. Characters are only balanced when all of them can get in a battle and dish out damage (very direct like fireball casting wizards and sword swinging Fighters, or indirect like Bard`s using their songs to improve the other`s combat abilities).
Unfortunately, many groups may find D&D and other D20 based systems to become boring, because D&D is very much about combat. But I think may DMs do also find a way to handle this. They won`t be able to use many published materials (especially adventures that use special "power" assumption", but with some creativity, everything is possible.
If you want "less power", you might perhaps wish to try "Wheel of Time"...