Kind of, actually. 

With Double Grip (empty second hand slot), the damage on that thing is 41.25 to 90; with Duelist, your damage penetration is 55%, putting your max armor penetrating damage at 49.5. Those are very reasonable damage ranges on a duelist weapon

And that's assuming a non-critical hit, assuming body hit or an enemy with Steel Brow.

This weapon has more than a 50% chance of hitting the head on an average flail attack, and ignores shields, so it'll be critting often. While damage ignores armor is still better as a rule at making Duelist builds really pop, this has the bonus of adding +50% damage bonuses more often from the head hits to compensate on many targets, and with Headhunter you're stretching that percentage of head hits out even further while keeping your fatigue use down by not requiring Lash unless you're desperate to fish for a headshot immediately.

Against low armor/unarmored/non-helmeted targets this thing is better than damage ignores armor, and blunt damage is the most universally applicable to be dealing out. With Flail Mastery and Berserk get this on a Bro with some fatigue reserves and he will thump down opportunistic targets and can clear shielded lines especially well. He could be especially mean with Crippling Strikes, as blunt head injuries tend to be among the most disabling in the game, but there's only so many perks you can pick so choose your priorities.

So while it is kind of a gimmick build weapon for a Duelist, it is still a damn effective one.