The first four ARR Beast Tribes (Amal'jaa, Slyph, Sahagin, and Kobold) only go up to Rank 4 via the repeatables. The Ixali go up to Rank 7 via repeatables, as well as having enough quests that you could use all 12 just on them.

ALL of them auto rank up to 8 after doing a special quest for getting them up to Rank 4 (7 in the case of Ixali.)

The Vanu and Vath quests, meanwhile, go up all 8 ranks with their repeatables, and you can only do 3 per day unlike the rest that give you atleast 9 quests per tribe.

For Vanu it'll take you about the same amount of time to get them up to rank 8 as it does to get one of the ARR up to its max rank. Vath takes a bit less time since they decided to start them at Rank 3 AND they give 70 rep instead. Thats currently the only one that could be considered "unbalanced" in comparison.