Storm Raven said:Realistically, you don't get that many useful net spells out of the combination. For example, take a typical 9th level Mystic Theurge (Cleric 3/Wizard 3/Mystic Theurge 3) vs. a 9th level single classed Cleric. Let's give them both a 20 Wisdom (accounting for a reasonable initial score, plus magic items and level adjustments), and just to make it interesting, we'll give the Mystic Theurge a 20 Intelligence.
Their spells, by level:
Cleric
Divine - 0th: 6, 1st: 6+1, 2nd: 5+1, 3rd: 4+1, 4th: 3+1, 5th: 2+1
Mystic Theurge:
Arcane - 0th: 4, 1st: 5, 2nd: 4, 3rd: 3
Divine - 0th: 5, 1st: 5+1, 2nd: 4+1, 3rd: 3+1
So, let's net this out
Cleric - 0th: 6, 1st: 6+1, 2nd: 5+1, 3rd: 4+1, 4th: 3+1, 5th: 2+1
Theurge - 0th: 9, 1st: 10+1, 2nd: 8+1, 3rd: 6+1
Net Theurge: 0th: +3, 1st: +4, 2nd: +3, 3rd: +2, 4th: -4, 5th: -3
Actually, you gave the MT a third level divine domain spell he doesn't get.
Net Theurge: 0th: +3, 1st: +4, 2nd: +3, 3rd: +1, 4th: -4, 5th: -3
For all intents and purposes, he is giving up 7 4th/5th level spells to gain 8 1st/2nd/3rd level spells.