Terpderp has been collecting dust for quite a bit now so I grabbed an Air Knife for science lol. Should I have grabbed an Onion Sword instead? Probably, but I rarely get to use dancer for anything so I don't really care for the utility tbh.
Locus Imps with lv.10 box step and dia III. No food, building flourish, attack buffs, etc...
Terpsichore + Air Knife ws average: 17,832
Terpsichore + Twashtar ws average: 17,281
Honestly a pretty nice offhand option for Terpderp PK spam. Weaponskill averages were nearly identical, but Air Knife has higher white damage with it's additional effect. It has a nice chunk of evasion for tanking and the 10% haste is actually kinda nice for tanking sets to stay haste capped. Aeneas/Twashtar + TP offhand still blows it away though. It's not even close lol.
Since the additional effect is magic damage it is also boosted by
Orpheus's Sash. However, it is not boosted by any form of normal magic attack bonus.