LokiDR,
You might consider applying bonuses and/or penalties to feinting just as for normal Bluff checks. This way, if your player just says "Ow, my arm" you can apply a lameness penalty or at least no bonus. Expending valuable ammunition to fire misleading shots or thinking up creative feints might result in a bonus, or at least no penalty. Also, if the rogue attempts to feint repeatedly in a combat, or even feinting an opponent that has heard about the party's tactics, you can put pressure on the player to come up with novel, creative feints in order to avoid penalties for multiple attempts. Or, if you don't like penalizing him, you can allow bonuses only if they are new. Such a system of incentives and disincentives may result in the player working harder for those feints, as he tries to think creatively to maximize the odds of it working. This also would result in more colorful oratory and roleplaying during combat, which often devolves into pure wargaming. This might also make for more entertaining memories, as people will fondly recall the best and worst of the rogue's combat feints.
--"Remember the time when Luna stuck that evil wizard in the throat after firing off a quick feinting shot at his rat familiar?"
--"Yeah! That guy freaked out so badly when she said she was gonna roast it right on her bolt like a spit. He left himself wide open when he cast that lightning bolt. Good thing she dodged it!"