Assuming you are actually playing this, I think that levels 10-14 are going to be a challenge -- you will be way behind on spells and on attacks. You'll have a flexible range of cantrips available to you, but not as much flexibility as some other classes class combinations.
That's the balance comparison. Take the cleric class, and replace the spell list with the wizard list. Now what changes (if any) are needed to make it balanced with a standard cleric? Apply any. Now pump its melee combat power up and drop it's spellcasting a bit. I still ought to have access to spells from at least the 7th level list. That's about what I want out of my fighter/mage.
Remember you are giving up the threat of an opportunity attack when you cast shield, which is one of the fighters useful methods of holding the line. Last time I used shield in combat all the creatures, realising that my character was now unhittable and also distracted, ran past and nearly floored the wizard.I thought that then I thought I could probably mitigate it with one or a half dozen castings of shield.
In practice, this is not usually how it works out. You don't end up casting shield nearly as often as you might expect. I'm not sure what you mean by "other defenses." Protection from energy? Also doesn't come up very often, but extremely useful when it does.Of course after you've spent all your spell slots on shield and other defenses you're down to being a crappy fighter with rituals.![]()
I wouldn't hold my breath for an official alternative to multiclassing. They totally nailed the power level, and IMO would be extremely foolish to let it get any more "creative" than it is.
I should be able to make a character who is a little better as a front line warrior than a cleric and a little worse as a spellcaster than one--and use the wizard spell list instead.
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I still ought to have access to spells from at least the 7th level list. That's about what I want out of my fighter/mage.