Uhm,

Combat pretenders have a different role, arguably more benefitial than the 'stay at home' kind.

There are multiple ways to rid yourself of afflictions. And you can always get your pretender back; albiet without as much magical skill. Though if you take the talentless Wyrm, he can come back good as new only after 40 points of calling.

Combat pretenders help forge a game early, while rainbow/caster pretenders shore up the mid/late game for certain nations.

I am of the opinion that Rainbows are less 'useful' because when I start taking over a rainbow nation it's already all searched for me So I get all his goodies. Especially those back ones that he can't defend well. Whereas if you lose a combat pretender more often than not that place can be filled with another SC while you get your old one back at the expense of a few turns of priests.