I just started entering the goblin area, but dice based conversation doesn't give me confidence that is worth trying a diplomatic way, because if that fails I will be surrounded by a lot of them in good positions. I may send in a messenger alone though, and if they slaughter it, will wipe the entire hostile camp.

But who is Haslin, the druid healer? He turns red as well if we attack the goblins? Well, will try to knock out then, need that alive.

Just make a save game before trying things like this, everything should be a valid way, just being EA some could be missing or bugged.