Well its 2 net. You can keep Gale if that is what you are referring to, and Minthara is instead of Halsin. However, the loss of two origin characters is a significant loss of content, on top of all future content with the Tieflings.
This is a huge penalty without any significant upside. It also seems very unnecessary. The game even has a secret tunnel under the druid grove for the Tieflings to escape and its not like this is a completely implausible option given the druids were trying to evict them. If you didn't kill the Tieflings, it would feel more plausible that Karlach and Wyll would remain.
