According to Allakhazm forums, the drop rate is 1/10.
See
https://everquest.allakhazam.com/db/npc.html?id=6150.
Another forum on the original quest says quite common:
"Found one of the Baracuda livers from the first one we killed, but then started having a few problems finding any more. Enlisted the help of a guildie druid, who tracked them for us, and bingo! another liver on the 3rd or 4th kill. "
https://everquest.allakhazam.com/db/...tml?quest=1224
However, that same thread talks about it being rarer.
Thanks,
- Petel