
DeadliestPrawn |
Neither using the bite as part of a grapple check or as a standard-action single attack is "using the attack as part of a full-round attack", and thus the -5 penalty does not apply, even if used multiple times in a round.
In my own game, I have an abyssal bloodrager with claws who is considering grabbing animal fury through the Primal bloodrager archetype, granting themselves two claws and a bite whilst raging.
As I interpret the power, the -5 penalty is a restating of the normal penalties for using manufactured weapons alongside natural weapons during a full-attack action.
I would argue that all bite attacks are natural weapons, and the rage power says nothing about the bite being a secondary natural weapon, not to mention bites are usually primary natural weapons.
Bear in mind that one of the additional actions available to someone who's just maintained a grapple is automatic damage with a 1 handed weapon etc, and I think Primal Fury is simply saying the rager can forgo automatic damage dependant upon the grapple check's result, and make the attack first, potentially granting a bonus to the grapple. It might even be saying that this initial, bonus-providing attack is free, and even with a standard action grapple maintenance check, you can get automatic damage with the bite again if desired. Add to that greater improved grapple and one could potentially get 4 bites in if they hit with everything, or two bites and some movement, or any combination thereof.