Which parts, specifically? I'm quite familiar with the MT and the various ways to build one.
The usual problem with a mystic theurge is that you can be quite weak in the mid-levels, say levels 5-9. This applies to buffing and debuffing too; haste & slow are 3rd level spells.
If you're doing the wizard 7-8 w/faith magic / divine caster 1 / mystic theurge build this isn't a problem, but then your cleric or inquisitor (or other divine) spellcasting isn't going to be a big deal.