From what I've read a whip trains dex.
Current character (who lost her spear of mayhem to a trap) found a whip of devastation (5d3+6) which I've used it a bit but no dex increases.
Is the training a very small amount or does it mainly affect low dex (19/35 currently) ?
I did also find not one but two bloody daggers and they seem more effective in regards to pure damage output (str 17).
I assume the whip is about as flimsy as the daggers in regards to item destruction.
On my way to dwarf town so no garantueed weapons yet.