I haven't played the 'evil' route in a while and only once at that, but I remember failing that persuasion roll, did they change that in one of the patches? I like to think I treated her well too, though I was roleplaying a lolthsworn.
Or just become a companion; there is already a plenty of reasoning for this to happen. Even for non-evil playthrough.
I'm not sure how non-evil runs don't end up with her and the rest of the goblin leaders being dead? And If you bypass the whole conflict you won't have spoken to her in the first place.
If you check YT the DC is 1. On my gameplay, I had it at both 5 and 1, in different circumstances. The 5 was when I had +4 buff from cleric of Loviathar, so I guess it's bugged. Probably for that particular interactions DC is made higher, not lower, if you have some positive effects.
For now, "good" run is always lethal for Minthara. Even if you knock her out, either game thinks that she is dead or Tieflings finish her off. That's clearly a result of unimplemented options.
I have written in other posts, why there is a good chance for her to appear as a recruitable companion in future; even for PC who isn't exactly roleplaying "evil" side. If you are interested in that being explained once again, no problem.
It's completely against her character to fight until death too. Several times in game we are told how much she values her own life, that she is pretty cowardly and not really an honest believer in the cult of the Absolute. But like I said, it's 110% the result of EA.
Pretty big hint is both the existance of knockout and the fact, that prisoner cage exists in our camp. Potentially holding her as a prisoner and persuading her to join our case seems to be pretty real and logical. She also doesn't happen to know that a tadpole is inside of her head.
I will repeat what I have said before, just as a little clarification.
You remember though, that:
- "I do not intend to lead a suicide charge"
- "Goblins are expendable, I am not"
- She spent her whole life "anticipating knife in the back"
- Via mindreading, we get to know that she is pretty cowardly, we can even call her a coward afterwards.
She clearly values her life to a great degree and isn't the most brave person. Also, if defeaten, but not killed:
- She still needs protection from possible drow assasins, as she is an ex-Lolth believer
- Enemies are everywhere, she has no friends as well
- I do not think that Absolute tolerates failure, returning there isn't an option.
At first, she wouldn't join you out of sympathy, to quote Lae'zel - "Practical choice". That would be the reason. She is said to be very intelligent and her possible knowledge of Absolute could be put to a great use for PC. I'm pretty sure she could realise that.
We get to know too, that she isn't exactly the most honest follower of Absolute, probably she sides with them only for power.
Arguments like "only 20% of players would do this" do not make sense, because BG3 is a Larian game and those are always very well constructed and full of often hidden options. Examples include:
Divinity 2 Original sin: You can defeat Dallis in Act 1; Kniles has special voice line after being teleported into closed cage;
Baldurs Gate 3 - almost every corpse has something to say, if forced to do so via spell.
Take look at this if you wonder, how neutral/good run could still result in Minthara being alive and in possibly good relation with PC.https://forums.larian.com/ubbthreads.php?ubb=showflat&Number=748888#Post748888
The most important posts are the first one and the 3 rd last one, which is basically a summary of entire long discussion.