Dynamis Tavnazia Trouble: Tome 17

My best friend and I recently unlocked access to Dynamis Tavnazia with the intent of doing Arch-Diabolos. We looked up information beforehand about what tomes we'd need to pop, and where to get them from. We got 15 & 16 to drop rather easily. NQ Diabolos we got a pop for right away, but put off popping (so more or less had 14 by default) at first. Then we spent the remainder of the run (a bit over an hour and 15 minutes) trying to get 17 to drop. No such luck.

We double checked all information sites, and everyone confirms that tome 17 indeed drops from DC Nightmare Clusters & Leeches, same as tome 16. We chalked it up to just an unlucky first run. Cut ahead to today, we again went to Dynamis Tavnazia, this time aiming to work on farming tome 17 immediately after TE's.

Despite spending the whole run on clusters and leeches, we did not see a single tome 17. This is with my friend being on THF as well. Is the tome truly this rare, or are we doing something incorrectly? I'm hoping this drop isn't bugged or something of the sort.

Thank you for reading.

http://ffxidb.com/items/3486

This information is pulled directly from guildwork, so should be accurate. 3~4% drop rate, maybe it was just bad luck?

Thank you for sharing that data. While it probably is just that, it's still rather ridiculous that not a single one has dropped in a bit under 3 hours worth of farming solely those mobs (total so far).