Of course, delving deeper just makes matters more confusing
Leopard, Lion, Tiger, Annis Hag, and Leonal Guardinal all use their full attack bonus for a rake.
Skum use their secondary attack bonus (full -5), while Griffons and Sahuagin use their Multiattack secondary attack bonus (full -2).
Dire Lion uses full attack bonus without Weapon Focus (claw) added. (Claw +13, Rake +12)
Dire Tiger uses full attack bonus -1... two less than full attack bonus plus WF: Claw.
And then there's the Fleshraker Dinosaur from MM3, who doesn't have WF: Claw... his rake is either full attack bonus -4, or secondary attack bonus +1... either way, it's weird.
-Hyp.