Halsin says that for two reasons, either goblin leaders were not properly killed which in your case you did or because he needs to be in grove to tell his druids like Kagha a piece of his mind, that sort of business.
Something just went wrong with your game per say and this is not some new bug, its been an issue as far as 3 months back too, but for those players I have no idea what kind of order they did quests in.
Is possible that something bugged out doing quests in an unexpected sequence of order, not using any installed mods are you?
