Patch 1.2.1 is out as of October 31st, and with it came some pleasant updates and a not so pleasant bug. As of now, Necromancers are unable to generate corpses with the dummies in order to test out their builds.
In addition, neither the Minions of Necromancers or Companions of Druids will attack the dummies, all of which culminates in the dummies being a bit more of a dummy than they should be.
Uber Uniques Retroactively Rerolled With Perfect Stats Patch 1.2.1 Datamined Changes
Adam Fletcher, Global Community Development Director for Diablo, has responded to players and has brought some good news for Necromancer and Druid players. A fix will be out before long for Necromancers and Druids so they can use the new feature to their heart's content.