Training Dummies will be added to Diablo 4 with Patch 1.2.1 during Season 2! Blizzard has heard the community feedback stating that many other Blizzard games already give players meaningful ways to theorycraft game aspects like character damage or skill rotation — and so should Diablo 4.
Diablo 4 Season 2 Campfire Chat Liveblog Summary
With the introduction of Training Dummies in Patch 1.2.1, players will be able to spawn different types of dummies in what appears to be a private instance. According to the images shown during this week's Campfire Chat livestream, a «Configure Training Dummy» window will let players spawn Normal, Elite, Boss, Single, or Multiple Training Dummies:
Given the fact that Blizzard is actively working on changes around damage calculation and character itemization, having a meaningful way to test different aspects of character power that may have changed due to content updates will be very much welcome.