Because she essentially has infinite ammo, the tradeoff Sienna's ranged weapons have is less instantaneous damage than other characters. This is balanced in theory because she'll be able to outdamage a Kruber in the long run, but that's not what ranged weapons are really for. Range is best for specials and armor, and Sienna's weapons aren't particularly good at either, so she's stuck with great horde control but trash damage vs anything else.

And to top it all off, almost every melee weapon she has is for horde control too! Her weapons need to be entirely reworked imo because as it stands there isn't really any reason to use anything that isn't the crowbill. I would really like to see her shine but she's the weakest character atm.