Is this homebrewed divine version of Abjurant Champion balanced?

Question

I'm starting a game soon and one of the player normally plays an arcane spellcaster(usually wizard), but has decided to take a dip into the divine. He's particularly fond of the Abjurant Champion prestige class and its Martial Arcanist feature. He asked if a divine equivalent exists, and as established by my question yesterday, one doesn't. So I reflavored Abjurant Champion into the below homebrew class.

The general flavor of this new class is meant to be a divine templar-esque kind of fighter, A protector of the weak/shield of the innocent type. It is intended to be a prestige class for Fighter/Cleric or Fighter/Paladin builds, combining all the martial prowess of a Fighter with a Clerics or Paladin's religious pious nature. Basically a super-paladin without the alignment straitjacket.

Is this homebrewed prestige class balanced? Is there a better school to tie it to for divine casters?

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Stalwart Protector

The divine champion focuses his divine abilities both to augment his personal defense and to hinder enemy spellcasters. Perfectly suited for martial stalwarts who dabble in magic, this class offers characters the ability to improve their combat skills in ways neither soldiers nor spellcasters can. Requirements

Base Attack Bonus: +5

Feats: Combat Casting

Spellcasting: Must be able to cast 1st-level divine spells, and have access to the protection domain.

Special: Must be proficient with at least one martial weapon.

Hit die: d10

Skill points: 2 + Int

Class Features

Spellcasting: At each level, you gain new spells per day and an increase in caster level (and spells known, if applicable) as if you had also gained a level in a divine spellcasting class to which you belonged before adding the prestige class level. You do not, however, gain any other benefit a character of that class would have gained. If you had more than one divine spellcasting class before becoming an stalwart protector, you must decide to which class to add each level for the purpose of determining spells per day, caster level, and spells known.

Abjurant Armor (Su): Any time you cast an abjuration spell that grants you a bonus to AC the type changes to an armor bonus and you can increase the value of the bonus by your stalwart protector class level. Stalwart Protectors rely on Shield of Faith, Protection from X and similar spells instead of actual armor.

Extended Abjuration (Su): You depend on your abjuration spells to protect you in combat. Double the duration of abjuration spells you cast, as if you had applied the Extend Spell feat to them (but without any change in level or casting time).

Swift Abjuration (Su): Beginning at 2nd level, you can cast abjuration spells as a swift action, as if you had applied the Quicken Spell feat to them (but without any change in level). The maximum level of spell you can quicken in this way is equal to 1/2 your class level (rounded up).

Divine Boost (Su): Beginning at 4th level, you gain the ability to burn Turn/rebuke uses to empower your martial abilities. As a swift action, you can spend one or more of your Turn/ Rebuke uses to grant yourself one of the following insight bonuses for 1 round.

• Bonus on attack rolls equal to the number of uses spent.
• Bonus on weapon damage rolls equal to twice the number of uses spent.
• Bonus to AC equal to the number of uses spent.
• Bonus on saving throws equal to the number of uses spent.
• Resistance to acid, cold, electricity, fire, and sonic equal to 5 × the number of uses spent.

Divine Fury (Ex): At 5th level, you master the art of combining your militant and divine training. From this point on, your caster level in a chosen Divine spellcasting class is equal to your base attack bonus (unless it would otherwise be higher). For example, a 7th-level fighter/1st-level cleric/5th-level stalwart protector has a base attack bonus of +12 (and thus a caster level of 12th). You can apply this benefit to only one divine class to which you have added spellcasting levels by your advancement as an stalwart protector.

Answer 1

It’s weaker than abjurant champion, but should still be plenty viable

Requiring the protection domain is a rather stringent limitation, compared to just requiring at least one abjuration which you would need to benefit much from the class anyway. And the protection domain is pretty poor—the granted ability is OK but not stellar, since it has to be used ahead of time and could easily get triggered by something dumb rather than something dangerous. The only non-cleric spells on the list are mind blank and prismatic sphere—fantastic spells, no doubt, but only if you’re playing at the very highest levels of the game.

Moreover, by far the biggest draw of the abjurant champion is the combination of full BAB and full spellcasting progression. For your typical poor-BAB arcanist, that represents a benefit of +2½. But divine spellcasters usually get medium BAB, so the benefit is +1¼—literally half as much. And, for that matter, since we’re talking about a cleric—they’re the ones who get domains, after all—we can’t forget that divine power is available to fix any BAB problems they may have anyway, making the feature redundant.

The change to abjurant armor is actually really bad—now those deflection-bonus spells are much, much worse. It might be better to just let them keep their usual bonus, and just add an armor bonus on top of that, than to convert the bonus. Or the character will just have to resign themselves to skipping those spells, and using (greater) luminous armor from Book of Exalted Deeds for everything (which is what regular abjurant champions do, optimally). No matter what you do, though, the fact that a cleric could have trivially worn a mithral full-plate rather than cast any spell—an option not easily available to an arcanist—means that this feature is vastly less valuable than it was on abjurant champion.

Finally, divine boost costs quite a lot more than arcane boost does—spellcasters get a lot more spell slots than a cleric gets turn/rebuke undead uses, but on top of that the arcane version lets higher-level spells count, effectively, as much as multiple uses of turn/rebuke undead. None of the boosts are all that great, but the arcanist will definitely be able to use them more and more painlessly.

Still, we are talking about a class that advances spellcasting at every level—that means it’s really hard for a class to truly be bad. If divine fury convinces the player that it’s “safe” to lose spellcasting progression elsewhere, they’re wrong and that’s problematic, but if instead the player full well knows that losing spellcasting is weakening them, and they’re doing it intentionally, then maybe the improved caster level makes the result feel better—and that’s great.

Ultimately, a single-classed cleric is probably better off than someone using this prestige class. They would be free to choose other, potentially better domains, they would get to skip the mostly-pointless Combat Casting feat, they wouldn’t have to worry about getting a martial weapon proficiency (please just take the feat, the war domain is so bad), they could keep using non-armor AC-boosting spells, and so on. And the benefits aren’t that great for them—their caster level should be greater than their BAB anyway, abjurant armor is a bad thing, and in any event the whole concept of greater AC is just less valuable to characters who don’t have to worry about arcane spell failure.

Normally, for a prestige class, that would be pretty damning. But in this case, it’s really just a testament to the absurd power levels of the cleric’s options that most of these benefits turn out to be fairly minor, and that these restrictions actually turn out to be more than they’re worth.

I would have no problem with this in my game.