Ideas for Curbing High Level Magic Power

[Cosi]

I suppose I just don’t want the caster players to trivialize encounters with the spells once we are in the higher end of the level spectrum.

Casters trivializing encounters is an encounter design problem, not a balance problem. It's not particularly hard to put together an encounter or adventure that's still challenging for casters. In fact, if your party is ToB martials and relatively low op casters, you're probably fine in combat. Unless the Wizard has something like planar binding loops or simulacrum armies, a Warblade will do fine. Perhaps not quite as good, but easily competitive (my suggestion of offering a non-ToB Gestalt can help here, and give people access to non-ToB classes without losing power). Outside of combat it's not too tough to plot around caster capabilities, but once you do that it becomes very difficult for non-casters to contribute. An adventure that is built around teleport (in a way that is constructive, not just "screw you no teleporting") is one where Survival and Hide probably don't have too much use. But that's a problem that's a result of martials lacking abilities, not casters having them. So you should figure out how to get the Crusaders and Warblades some stuff to do in a high level adventure.

The one change I might consider would be pushing people towards classes like Sorcerer and Beguiler that have lists that are fixed when the adventure starts. From a balance perspective it's not a huge deal, but if you feel overwhelmed planning for caster capabilities it limits them slightly without imposing any unreasonably costs or warping things.

Or just play E10. Though you might still need non-combat goodies for non-casters. Maybe give them Adept or Magewright casting as a quick fix.