Vaxalon said:
Name them.
See how long it takes for the Mystic Theurge to buff himself up to the same attack bonus, saves, and hit points as the cleric has. At that point, the cleric is up by that number of rounds of melee.
I'm with the minority. I don't see anything wrong with the MT.
I don't want to get into an argument, as I don't tend to win them

but I would like to try to answer your question as I'm curious to know if the class really is that good or not.
Attack Bonus: Divine power. The cleric/wiz can have as low a bab as possible, but it's all made up for by divine power, and at higher levels persistant divine power.
Saves: Well, I generally prefer the tactic of not being hit over the tactic of buffing saves, but here's my take. As far as saves go, either character stands about the same chance as buffing them, so the only workable comparison is base saves. This guy'll have higher will than either of the other two would alone, what with three classes all having high will. He'll have lower base ref than either of the other two would have. He'll have lower fort than a straight cleric, but higher than a wiz... and not by all that much. Summary: this guy won't be avoiding ref saves without some buffs and he's more vulnerable to fort than a cleric, but not than a wizard. Saves appear to not be an issue.
HP: Hmm, not much I can say there. While there are a few spells that a wiz can use to buff his hps, there aren't enough to make up for the amazing lack that this guy'll be getting. I'd rectify this as follows:
AC: Wowza. As far as AC goes, this guy has all the benefits of both types of magic to keep him from being hit. Between Magic Vestment, Shield, Mage Armor, Haste, and everything else, his AC should skyrocket. Though this doesn't totally fix the problem of low hps (i.e. power words... suprise rounds... crits... etc), it generally can keep you far away from being hit.
I can see some problems of the class myself... the number one being that as a melee character, this guy'll have some problems. His HP will probably prevent him from going into melee whenever someone might dispel him. The second problem is that he'll be stuck taking feats that'll compensate him for his weaknesses. Spell Penetration and Spell Girding pop into my head first and foremost. The second third is that as far as offensive capability goes, he'll have his share, but it'll never equal someone who went for PrC's that better suit that purpose. Take the Spell Power ability (archmage, red wizard)... take Improved Metamagic (incantatrix)... this character'll lose out on all of them.
On the flip side, think of versatility. This person's a walking ball of abilities. He can cure, attack, buff, move(teleport or plane shift)... do just about everything that anyone would normally purchase items to do if they didn't have the ability themselves. Metamagic feats will probably be your friend, as you'll have two classes to get a lot of use out of. Crafting will also be majorly useful, as you have the ability to make almost any item in the game (no monk's tatoos *sob*).
So basically, you lose out on a LOT of oomph from a straight wizard's blasting power to get a lot of versatility. You lose out on a LOT of oomph from a straight cleric's ability to hit things in physical combat. You lose out on a LOT of oomph from what someone with other PrC's would get... depending on what beyond the DMG is allowed. You gain an absolute TON of versatility.
So if you value versatility, this class is somewhat overpowered. If you value sheer power... I dont' think there's anything to worry about. Because of this tradeoff, I'd like to see it in play before I completely crusify it.
