Unless Larian rewrote this part of the story in patch 5 what you posted about Karlach makes no sense. The way it played out in my game, Karlach doesn't know (or anyone in the party at this point, that is player's metagaming knowledge) that the mindflayer transformation will "fix" the infernal engine. She offers, because she is dying and feels that way no one else needs to sacrifice themselves. That is the opposite of clinging to life at any cost.
That anyone transforming loses their soul is a problem in itself, because you can learn in the game (unless Larian rewrote that part of the story) that the soul can be restored through divine intervention - but only if you play as Gale. Mystra will offer if you choose as Gale to turn into mindflayer. Withers however will not mention it, and there is no other way of the player learning that, so that they could e.g. use the high level cleric ability.
You are right about the first part. I forgot that you only learn the bit about Karlach's engine after she takes the tadpole. The same is true for Gale however since - unless I have missed something - you only learn that Mystra can restore his soul once you actually show up as a mindflayer in his origin to return the crown to her.
Originally Posted by Ametris
What the game actually shows us is that Gale is more heroic than the self-proclaimed hero.
Because Gale is awesome! And while I never intend to blow him up (other than using the cantrip instead of F8) I really like how almost casually he offs the brain.
And I do like the Avernus ending too, I just feel mounting resentment towards Karlach. ^^
