It is useful for fighting groups of minions but so is sienna’s melee and that gives temporary HP. But since it is so awesome it would suck to change it. How about adding a special weapon action to it. The special weapon action could be throwing it like a javelin and it becomes a ‘flame sprinkler’. But it uses all of it’s overcharge and can’t be used again until it cools off. And it hurts sienna slightly to pick it back up.
Capping out overcharge instantly is a pretty brutal downside for any but unchained, though i wouldnt be terribly opposed to adding something new to the staff to give it more flavor…ideally without buffing it to the clouds in the process.