Totally outside of RAW but here's an idea:
Because the hyena isn't very dense or hard, add a knockback feature to it. It would be like being hit with a big, furry, boney, yelping pillow. target takes damage, hyena take 75% damage dealt from the blow.
Knockback mechanism is as follows:
Target knocked back in a random direction 1 foot for every +1 bonus to strength the weilder has, rounded to the nearest 5ft mark. so a pally with a +5 mod knocks his hyena target back 5 feet in a random directionaway from the hyena weilder.
(This is of course providing that the target is the same size or smaller than the weilder of the hyena)