What we have so far in the homebrews is just the greater version, so I don't think we need growth until we do the lesser ones. I assume, like the barghest, the greater version shouldn't advance.
That sounds right to me, so shall we go on to skills and feats?
They can have seven skills at max - Diplomacy, Listen, Spot, Sense Motive and Knowledge (Arcana, Geography, Nature, The Planes) all seem tempting. That's eight skills though.
Max out Diplomacy, Listen, Spot & Sense Motive and split the remainder between the four Knowledge skills, or just cut out one of the Knowledge skills?
I think I'd just cut Knowledge (geography), to leave it the following skill ranks:
Skills: Diplomacy 16, Knowledge (arcana) 16, Knowledge (nature) 16, Knowledge (the planes) 16, Listen 16, Sense Motive 16 , Spot 16
Does that look alright?