Tzardok I should probably add these three optional bosses to the wiki. Something for my to do list.
I did the magical one kind of accidentally while I was poking at their weaknesses before the datamine so I don't have suggestions here. I know I brought Robin, Altina, and either Qum or Carina. I don't remember if the fourth slot was Carina or Qum, or Riala. I didn't find this one particularly difficult but pick any of them that isn't the left one and just hit it with weaknesses until it dies. Equip people appropriately before hand.
I will say that Altina using her AoE spells instead of single target did make a difference. Even with the damage being low, it still added up over time and if nothing else you'll chip away at the left one while targeting another.
The sexual ones took some playing around with my gear though. In the end I could only protect one of my succubi from Lust Death and Sexbind (Tormented Shield + Sexual Pin). I chose Nalili and then also brought Vhala and two others who did nothing but take hits.
Nalili - Combat Masturbation until Sexual Aegis, then Orgy of Blows forever.
Vhala - Unperson Aura, Defensive Rain x2, then Arrow of Abstinence whichever has more health. Reapply debuffs as appropriate.
If Nalili randomly targets one too often, switch to a single target attack and attack the one with more health with Vhala as appropriate although I didn't have to.
Of note, the Sexual Pin now resists Sexbind 50% so I basically had to try this until Nalili resisted the first AoE Sexbind and then the above strategy worked first time. I believe the Succubus Pin and Yarra's custom pin both block Sexbind 100%.
Iris' quest reward also blocks 50% if you choose the appropriate options (as above) although I chose another reward (Physical > Elemental). I started a thread on that quest + a discussion on which rewards people thought were best to choose if you're interested.