I, too, am bothered by it. Perhaps we could make it function more like a harpoon attack?
Maybe modify this to fit...
Impale (Ex): If a cadaver collector has successfully grappled a Medium or smaller creature, it can attempt to impale the creature on its back spikes by making a successful grapple check. Doing so is a standard action that does not provoke attacks of opportunity. If the collector successfully impales a creature, the creature takes 4d8+15 points of damage and is considered pinned. Each round, the creature takes another 2d8 points of damage as the movement of the cadaver collector causes additional pain to the impaled creature.
The creature cannot break free unless it makes a DC 28 Strength check. Success indicates the creature is free of the spike but takes an additional 2d8 points of damage in the process. Failure means the creature takes 4d8 points of damage and remains pinned in place. An ally can try to free an impaled creature with a DC 20 Strength check.
Once a cadaver collector has a creature or creatures impaled on its back spikes, it is no longer considered to be in a grapple and can attack other opponents without penalty. It cannot use its slam attacks against impaled opponents. Creatures that get free of a cadaver collector become its immediate and most urgent targets. It typically pursues such creatures exclusively if it has any chance of catching and impaling them again.
A cadaver collector's back spikes can hold up to 4 Medium creatures, 16 Small creatures, or 64 Tiny creatures. Creatures smaller than Tiny are too miniscule to be impaled on the collector's back spikes, although the collector can still deal 4d8+15 points of damage to such opponents by grinding them into its back spikes with a successful grapple check once it has them grappled.