I think it's believable, but only if done right. I mean, I just finished the Company of Heroes questline (I'm right about to fight Titan, oh boy!), and there's what, at least 8 or so of them you meet, with a significant number dead and/or tempered, with the survivors sometimes blind, crippled, or otherwise forcibly retired. Defeating Primals is messy business, to say it in a polite manner. Having to execute a longtime friend after they get tempered is enough to make me walk away from the business, I'd say.
