Hmm yeah, that would be the only way I could see the druids convincing the goblins to a neutral path. However, wasn't Minthara's motivation simply show of power through slaughter in the region? She may or may not be able to be reasoned with if that is her motive.
Confronting Kahga about the shadow druids doesn't have a path that works with the shadow druids. They just say kill Tav/PC even if you choose a pro shadow druid dialogue option.