The melodious truncheon proc was made unresistable a while ago but now it's not working on certain mobs. Ashenbone drakes in hate resisted it every single time. I'm not sure if it's because the drakes are giant-sized or because they have 100% MR but either way it should be working.
Old bug report:
http://www.project1999.org/forums/sh...ad.php?t=35610
thanks!
edit: I tried on another giant-sized mob (Ixiblat) and it worked fine, so I'm guessing it's just on mobs that are flagged as 100% MR