What seems apparent is that our statistical loot percentages are often not aligning with the indicated probability, and generally the outcome seems to be lower than projected.
I think we would need to know a lot more about DDO's RNG. RNG seed generation and advancement could be happening in just about any number of ways. What we do know is that it does hit clusters of excessive low numbers and sometimes clusters of high numbers.
I once received 130 reaper fragments in a single weekend, where normally (doing the same stuff) I average about 10, but sometimes get 0.
With a guildmate, we once ran soul splitter chain and both had a named item and an artifact drop in every single quest.
It just really seems like the RNG skews for or against the player for any uncertain duration.