This has probably been suggested multiple times, but here goes.
Give Druids, Sorcerers and Necromancers the ability to simultaneously carry both 2-hander as well as 1-hander&off-hander. Player can then choose which weapon is used by which skill, much like it is with barbarian.
One of the balance issues in the game since the beginning is that both Barbarians and Rogues can have multiple weapons as stat-sticks whereas Druids, Sorcerers and Necromancers have to choose between a 2-hander and 1-hander/off-hand. This makes balancing the game a lot harder since Barbarians and Rogues will always have more tempers, legendary aspects and unique items giving them more variety for strong builds.
Barbarians could still have access to 4 weapons making it their special thing, but every other class should have access to one 2-hander and a 1-hander/off-hander.
I promise you not only will the weaker classes be more in par with the Barbarian, but they will be much more fun to play and easier to balance going forward.
too ignorant…its no hope here…