I need to make a pyre ship using one of those bones to complete the fremennik diaries and I was wondering if anyone had an estimate of the drop rate of those bones from mith drags.

It's much quicker to just rummage the skeletons or killed Confused Barbarians. You get mangled bones instead of chewed, but you save a lot of time.

Thanks for the help that's alot easier...

Confused barbarians drop mangled bones 100%, so go with that.