First piece of advise. Don't ban anything because doing so would be stupid. The splat book classes are lame compared to the core casters and nobody will dispute that. The broken spells are easy to fix, just say no, or tell your characters that if they use them, then the spells are fair game. I run pathfinder now, so most of those spells have been retooled, however, in 3.5 none of my wizards had ray of enfeeblement. If the party wizard used one, even one, he would eventually be layed out by a maximized empowered RoE and be knocked out of a fight...because I'm mean like that. Easiest way, say no.

Second. High level casters are governed by a "higher power" so to speak. Druids go off to commune with nature and can be as viscious or tranquil as the natural world. Wizards and Sorcerers seek out more magic, focus on teaching the craft to the "new blood", or delve into research to learn the secrets of something. Clerics have dogma and a church/god to answer to. High level clerics often times, in my games and in every game I've ever played in, become priests and teachers within the church. They are surely powerful, but are even more adhearent to the wishes of their gods. Lastly on this note, does your world have dragons or demons/devils. There is ALWAYs someone bigger and badder that wants to steal your cookie.

Another alternative is to say that full casters are rare in the extreme. That way, the PCs can play them, but there isn't a cleric or wizard in every town. That also means that the services provided by casters is in high demand, and not easily squandered on a battle field, that is what soldiers are for.

Reading these boards is a bad thing for most people since most players won't powergame/optimize/munch their characters and won't rules monger you to death either.