The game does let you have them both in your party, you have to either ignore the grove or solve the problem through Kagha's shadow druid questline. You can even ask her for her opinion on Karlach, but since the refugee smith won't be available, I'm not sure where that leads (I paused that save and currently just going with the "intended" goblin raid way). But yes, a lot of this seems unfinished or cut and I really hope we'll get a Minthara expansion, she's the perfect companion for my drow mc and I'm obsessed :c
