10th(ish) Level - Balancing Magic vs Physical fights

The truth is, you're absolutely right. 3.0, 3.5, and pathfinder all have this problem. At high levels a spellcaster has way more power and more options than a non-spellcaster. The first step is to realize that this really is the case, the core classes are not balanced at all. And other classes produced likewise arn't. 

The gaming community has identified that these classes fit into "tiers" of power and usefulness. And if you want the long explanation it's right: here

That link also includes recommendations about how to handle it, which include things like allowing characters with weaker classes to get more benefits, or even get two weak classes instead of 1 strong one, or just not allowing the strongest classes. The most important thing is to talk to your group and see what they want to do. If somebody accepts their class is weaker, and still wants to play it without any changes they they can do that, but it should be an informed decision. 

The other thing you can do is look for other classes. There are a ton of version 3.5 classes out there, a bunch of ones for pathfinder, and a huge supply of "Homebrew" classes made by people like me and you that are better balanced than the regular classes you'll find in the core rulebook.

The other thing you can do to make it a bit easier, and one of the simplest fixes, is to give everyone and everything spell resistance equal to 10+their level. This gives spells a bigger chance to fail, though it doesn't entirely balance things out it's a good start.

Hope this helps!

I had never thought about it, but I like the idea of ensuring that it is an informed decision; really, they should tell you right out of the box that a Druid or Cleric at 20th level makes the rest of the party inconsequential, especially because, while Pathfinder toned it down some, they didn't actually fix the problem.

Sadly that link doesn't work for me- I'd love to read that forum post!

Thanks!