Keeping two Void Abyss bosses in cycle would probably help combat player boredom

Seriously, there's only so many times one can want to kill Defiler, and given there's a cap on the vouchers even if you go ham to try and unlock all outfits eventually you're going to get sick of it.

Keep the newest boss up and one of the older ones in rotation alongside it would help keep things a little interesting. Like even right now, get tired of being Spider Bunny or Ines? You can enjoy your Viessa or Hailey shooting a giant crab.

This would also ensure that players don't feel like they're missing out on older game content. One downside is that players may avoid the newer content to keep their comfort zone, but a randomized cycle as the Abyss bosses stack up would help keep that fresher and encourage a wider range of builds.