Mobs not dropping correct items?

Hi, I am still new and got a question on droprates on Warmane vs the Wiki.

I have been trying to get this formula (https://wotlkdb.com/?item=22551) from these guys (https://wotlkdb.com/?npc=20136#drops).
Every guide on the planet points me to these mobs. I have been trying to get this formula for the past 2 days and if the drop rate was a 1.5, I think I should be able to get it already.
I have already looted 15 [Arcane Tomes] which has drop rate of 1.8.
Also got bunch of 0.01 droprate items and bunch of other items that are not mentioned on the wiki.

Example:
Got this recipe (https://wotlkdb.com/?item=35294), and the mobs should not drop it according to the wiki.

Thanks for any clarifications or ideas on that :)!

There is a world drop version of that recipe which is probably what you got: https://tcubuntu.northeurope.cloudap...ow/?item=22926

Regarding the main question, some drops are bugged, but sometimes one just has bad luck. It is also possible that the drop chance of Arcane Tomes is boosted but the recipe's one is not.

Thanks, right the Arcane tome might have boosted drop rate, true.
Also got 11 other items that does not drop from this mob, not sure why this is, but these items are non important (greens / greys random weapons / armors).

Will try to get it for a bit more :D, will see