I sent the below e-mail to WotC (custserv@wizards.com) and I am asking you folks to write a similar one as well.
The Mystic Theurge is extremely over powered, particularly at high levels. Compare it to a wizard...
Wiz20 vs. Clr3/Wiz3/MTh10/XyZ4 (where XyZ is another PrC that grants +2 caster levels per XP level) = no contest ...even: Wiz3/Clr3/MTh10 (a level 16 PC) is a gross PC. That's level 7 spells in 2 classes folks! Quite the badboy at level 16 and it can be of any race without an XP penalty!
Worst case scenario is you wait until epic level to gain two more levels of MTh and 9th level spells, example:
Clr3/Wiz3/MTh12/Geomancer4 (w. geomancer levels split between Clr & Wiz).
With this worst case scenario, I'm level 22 (rather than 20) before I have max spell level in these two classes! This is a big differance from the 34 levels it use to take to get this.
Please do not go foreward with this class as is.
Sincerely,
Platinum