Imo that is not a priority, and only something worth considering when Chernobog has already hit capped damage with buffs/debuffs and your other Himes are catching up with the upgrade of your weapon grid. Also I did mention it might be "more worth it" when we finally get Dark Rags, and you are able to give her triple Tiara. Pluto is decently fast, but would probably need the 15% DATA from Tiara to match your team efficiently.
Edited:
I agree that "at this moment" it's not something he has to consider ASAP, and probably won't for a lil while. It's mainly because he has AW Satan, Thanatos, Osiris and wants to run a fast team with Shingen that I recommended Pluto for later on.
Chernobog is very strong(carries my dark together with Kali) but considering how we will eventually be getting debuff immune contents, the Lack of buffs might hurt. So it kinda felt like replace Cherno with Pluto at that point, which his weapon grid by then would be upgraded would benefit him well. Also, assuming he can get fast bursts, since PF is used every other full burst, it seems that Pluto could rotate buffs with PF for bursting(or even stack together).
AW Satan+Thanatos provides AC(15+20) frames Def Down and Drk RST(10) down which is useful for bosses he can debuff, and against immune they are the fastest(that I know of) himes for running Shingen. At least that's what was on my mind when I recommended him replacing Chernobog with Pluto in the far future.