I agree on that...
Firstly, if you're a pure build dueler as I am, you can't do the Charlatan job till around level 60 before item sets came out. With this set, one can, but unfortunately for ranged fighters, this complete set does very little for us. Yes, we can only use the 5 items without the Acid, but then we don't get the shooting bonus.
Secondly... It's acid in a bottle. Why the heck is it melee anyway? Do I have to apply it to my opponents face? Be realistic. I'd throw the bottle at you, which is a ranged attack. Take the boomerang for instance? It's the same thing. Yes... I could hit you over the head with too, if I would somehow be able to walk parallel to the floor.
The class in which the item falls would only make sense if they intended for duelers not to use it as a dueling set. But why would we. A good coat alone makes up for what we gain from the set in shooting. It would't be a great set for dueling, we just wouldn't be as vulnerable as we are now. The real bonus would come from the rest of the perks... but is it really such a bonus considering you can only wear a complete set at level 45?
I think this weapon has been placed in the wrong class. Maybe we're lucky and by the time the next sets come we'll be shooting knuckle dusters at one another.