I know certain items have different drop rates within their category, but some of the groupings seem super skewed. For instance, the set/unique axe/mace/spear echos, have 29 items in them. But bow and quiver only 14. Staff and scepter only 14. Makes the already grindy task of farming for specific uniques with LP, even harder if you are going for something in the bigger sets. There is always going to be a small variance with loot pools. Most are around 20, but having one literally double the size of others feels really bad.
Stuff like this is always just a snapshot of the current state of the game, when they will implement more uniques, this might change already.
On top of that maybe they will add more timelines and maybe splitting up those item type rewards further.
If you divide the numbers further into items that are only for certain classes or certain builds the numbers get even worse :).