Career specific weapons are a great way to make careers distinct from one another. With the ease of swapping careers in this game, career specific weapons add to the flavor of one career more than they take away from the character’s weapon selection as a whole.
A great addition to Sienna’s arsenal, that would make the Unchained feel more distinguished would be a flaming flail. A censer is a container used to burn incense, often danged from a rope or chain. There is an instance of censers used as weapons in Warhammer in the case of Plague Monk Censer Bearers, which would be an awesome enemy unit by the way.
Her charged attack could have indefinite hold duration similar to the flail, and could unleash a whip of flame on a strike similar to the fire claw portion of her charge attack with the flaming sword on the first attack and an overhead swing attack with decent range and a linear collider on second charged attack. Her quick attacks could be a 4 item chain with two alternating diagonal strikes follow by an upward swing and a whipped around horizontal swing. Her push attack could be a left to right horizontal swipe.
It would be a fun weapon to use.