I started the Vath quests yesterday and picked up the first three, but didn't do them until today. When I picked up the next three after completting yesterdays, I checked, and somehow I am rank 3, Friendly.
I never completed the first two ranks or got any of the quests. It appears I just somehow skipped to rank 3.
The Vath shopowner also says I am Friendly rank. and I need to get more quests to rank up past it. I have the achievement, too.