Mystic Theurge for Red Hand of Doom...bad idea or actually playable?

[Giegue]

As the title asks. The party I am joining needs both a divine caster and a skillmonkey but due to complex RP reasons I cannot sum up easily I want to stay away from a cloistered cleric build. Somebody in another thread thus suggested an archivist/Beguiler Mystic Theurge. I'd obviously take Able Learner, to keep beguiler skills as class skills, and using alternate source spell to take MT at level 5, being a Beguiler 1/Archivist 3/Mystic Theurge 1 at the start of the campaign. However, I am not sure if this is "worth it" or not, and would like people's opinions on this. Would this build be too "underpowered" or would it be just fine for the group. Just so you know, the rest of the party consists of a barbarian, monk and generalist wizard.

Any thoughts or opinions on this would be appreciated.

[Eldonauran]

If you use early entry tricks to qualify for Mystic Theurge, there is almost no downside, only the feat tax and the loss of one caster level. Even more so when you make a single attribute your casting stat.

Without early entry tricks, a Mystic Theurge isn't horrible. It is simply not as powerful as a single classed caster. If you base the worth of a class on the best it can be at every given level, Mystic Theurge will always be the lesser choice.

Since you already have a devoted spellcaster (generalist wizard), a Mystic Theurge is a great asset. Have Cure Light Wounds on your spell-list? Can heal with wands. You get the ability to uber buff your party members with your many lower level spell slots.

[Giegue]

Yeah, and I can still make a "passable" skillmonkey because archivists get 4+ Int skill points which is enough to boost the main skills I need on an int-based class.

[Waker]

You might benefit from using an Illumian with Naenkrau as their sigils. Improved Sigil (Krau) is useful for a theurge to bump up the level up spells without actually occupying a higher level slot.

[Giegue]

Yeah, but I HATE Illumians with a passion. I've pretty much thrown this idea away since alternate source spell doesn't work with beguiler.