Diablo 3 RoS: Unity trick
This is a well known trick that greatly increases your survivability in solo game. Many people, especially those playing melee classes, use this trick in high torments / high level greater rifts.
All you need are two Unity rings (one on you and one on your follower) and a legendary follower relic that makes your follower unkillable (Smoking Thurible, Skeleton Key or Enchanting Favor). Unity ring makes damage you received share with your follower. However, since your follower is unkillable, he/she is not harmed in anyway. The result is you are taking 50% less damage!
Some people think this is a glitch or even exploit. However, this trick is well known to Blizzard and they have not nerfed / changed this so far. In my opinion, they might even intentionally allowed the combo to work when designing these legendaries.