Or not? How exactly is unity applied?
I think: after all damage reduction, the remaining damage are equally shared by all those who wear a Unity.
In solo, if both you and your follower wear the rings, then 50% of your damage taken will go to your follower, and vice versa. i.e. your get 50% of the damage taken from your follower too. So, don’t forget to equip your follower a “can’t die” token, which is effectively same as “take 0 damage”.
In group, if all 4 players wear unity. Each player shares 75% damage to other teammates, but also recieve 25% of damage taken from other 3 players. I don’t think any group want to do that.