I am a 75 ranger and started at dubious, as did my 68 necro. I killed one bird, and became threatening. It would seem I was low dubious to start. From what I see of this faction, and King Peleke faction which is related, there is no way to improve it. I did all the other quests I needed on this island first because I thought this would happen, and why get adds when I didn't have to get them.