After griping about the sequence of 4 stars and how it seemed the same batch keep getting repeated, I decided to track back to when the 2 star essentials started, (to my knowledge) for the 234 essential format, which was Thick as Thieves on 5/7/15. They list as follows.
05/07/15-05/12/15 Thick As Thieves 4 
3
2
05/11/15-05/14/15 Dark Avengers 4
3
2
05/14/15-05/21/15 Hulk 4
3
2
05/21/15-05/24/15 Simulator 4
3
2
05/24/15-05/28/15 Deadpool V MPQ 4
3
2
05/28/15-06/04/15 Gauntlet 4
3
2
06/01/15-06/04/15 Juggernaut 4
3
2
06/04/15-06/12/15 Brotherhood 4
3
2
06/11/15-06/19/15 Prodigal Sun 4
3
2
06/18/15-06/22/15 Unstable Iso 4
3
2
06/22/15-06/25/15 Oscorp 4
3
2
06/25/15-06/29/15 The Hunt 4
3
2
06/29/15-07/03/15 Venom 4
3
2
07/02/15-07/06/15 Simulator 4
3
2
07/06/15-07/10/15 Meet RG 4
3
2
07/09/15-07/17/15 EOTS 4
3
2
07/16/15-07/21/15 Thick As Thieves 4
3
2
07/20/15/-07/24/15 DA Heroic 4
3
2
07/23/15-07/31/15 Hulk 4
3
2
07/30/15-08/06/15 Brotherhood 4
3
2
08/06/15-08/10/15 Deadpool 4
3
2
08/10/15-08/13/15 Juggernaut 4
3
2
08/13/15-08/21/15 EOTS 4
3
2
08/20/15-08/25/15 Unstable Iso 4
3
2
08/25/15-08/29/15 Oscorp Heroic 4
3
2
08/29/15-09/06/15 Prodigal Sun 4
3
2
09/06/15-09/10/15 The Hunt 4
3
2
09/07/15-09/14/15 The Gauntlet 4
3
2
09/10/15-09/18/15 The Hulk 4
3
2
09/17/15-09/22/15 Meet Rocket 4
3
2
09/21/15-09/25/15 Venom Heroic 4
3
2
09/24/15-09/28/15 Simulator 4
3
2
09/28/15-10/2/15 TaT 4
3
2
Unknown Date Brotherhood 4
3
2
Unknown Date PVE Anniversary 4
3
2
Notably, the 4 star repeats are 3 for Iron Man, Invisible Woman, and Fury, with 2 for Wolverine, Elektra, Professor X, and Kingpin.
The 2 star Repeats are 3 for Thor, Marvel, and Torch, with 2 for Cap, Wolverine, Mags, Storm, Hawkeye, and OBW. Notably, Daken’s shut out, and the only time Bullseye and Moonstone appeared was after recent changes to their powers, and Ares fell in to the villain set for the latest Deadpool round.
There were, for obvious reasons, no 3 star repeats.
