I think she is a good character to have. It gives players someone to hate early on and gets people more emotionally invested in the situation. Also, Tieflings are treated like crap in most places, druid grove is a good introduction to this.
My point is that Kagha and her followers are mad about something they could eaily solve themselves but have chosen to be xenophobic assholes for a reason the player does not understand. I doubt you are supposed to hate Kahga to the level where siding with her is just irrational, right?
I actually found more incentive to act on their behalf simply because of what happened. If the situation was just a simple bit of dislike between the two groups then I would have disregarded it entirely and continued looking for a cure. Would help them with the goblins later so I was not at risk of endangering everyone.
The Tieflings are totally in the right and the druids totally in the wrong. There is no incentive IMO because there is no rational decision making behind not helping the refugees. The evil / goblin path notwithstanding as there you simply murder everyone in the grove for vague religious reasons.