According to wiki

DOS - 500 000
DAO - 3 000 000
Diablo 3 - 30 000 000

Of course quantity does not mean quality but just some market data. Not shabby for my personal jewel DAO. Provided it is so old.

DAO had a curse of its own. It came very late to the community but when it came it was ahead of its time. As we later observed.

Here is a video from the lead developer of DAO on designing the combat mechanics

https://www.youtube.com/watch?v=tAwZZVFnqp0

To Larian, please pay special attention at 3:50