vorpal

does anyone know what attributes the Vorpal Scythe WS depends on for damage? during exp last night this WS was doing crap dmg about 3/4 times. i would do one for 300+ dmg, then the next 2-3 would do 27-100 dmg. 27!@#!@# WTH!! how can this WS do less dmg than a regular attack?! i'm really...