@Shax
But the only variable you have mentioned is 'current need', which you back up with a small sample size of your specific raid rewards. Serious question, can you remember what item your roster needed the most when you first recorded your raid rewards in September?
The item that is most needed by me at the moment, based on the ingame tool of who can currently equip it, is stun cuffs. I can currently equip these to 21 characters, and sometimes more than one set is required.
This has been my most needed item for at least the last 6 months. Therefore the need for this item is not dynamic. For this to change, I would need to farm or buy this cuffs until I no longer needed them. Which would take at least another 4 months to even make a sizeable dent (not factoring in that further improvements to my roster will further increase the need for this item).
I therefore don't agree with you that the 'current need' of an item is as dynamic enough to make an impact on the drop rate of an item as you originally suggested.