I would like to see more than 6 abilities. There is nothing wrong with relatively passive abilities (monk auras) especially when they are made with an activation ability like Diablo 3 but I want monsters and skills to work together so that we can have a game that requires some situational use of attack skills. With 6 skills, Diablo 3 kinda boils down to 1) generator 2) main damage AoE spender 3) movement ability 4) damage reduction /CC clear 5) short cooldown damage boost 6) usually an ultimate skill, sometimes a third attack that groups enemies or a second choice from 4 or 5.
There is very little flexibility there. It basically comes down to using 1-3 skills to “actively” do damage. The game isn’t really set up for requiring dynamic play anyway but I’d like to see Diablo 4 do better in that category as well. By D3 standards having 3 “active” skills is what I’d consider interesting.
If you give at least 8 abilities, there is room to have a fast hitting attack that you use mostly but also have a slow charge up ability that is more effective for slow moving heavily armored opponents.