Well any thing where you have friends as a strong connection does work well as an RPG, but Succubi have a lot of powerful mechanical advantages you can make use of.
Especially if your succubi are anything like the Soulcatchers in my games, commanding both a vast array of powerful Archonfire spells (demonic magic) and Sensual / Mind Control spells, they also have incredibly ability with their physical form, one example of one of the more notorious of these is Esperia Frostwhisper, and she's terrifying in battle.
http://www.youtube.com/watch?v=Jpf0HbuxreE
Why is she terrifying?
Multiple reasons, I'll list the most prominent ones.
Reactive abilities: She responds to the players usual methods of escaping harm by making doing such dangerous to even entertain, should the player try to sprint, they are immobilized for 3 seconds, should they try to shadow dash, she teleports behind the player and kicks them for 10 damage, this also sends them a few tiles in the direction facing, which can quickly mean trouble in an encounter of this sort.
Thirdly, any attempts to use anything but melee weapons on her are rewarded with a laugh and a kick in the back. Making it feel very much as though Esperia has more control than the player does.
Psychological Torment: Esperia is dripping with malicious intent, and she makes no effort to hide what a villain she is, at least not in this battle. The battle begins with her declaring "It's been too long...", and all of her battle mechanics have a pinch of VA to make her feel very real, lines like "Run, kitty-kat... RUN!" and "Realize... HOPELESSNESS!" are sad with such enthusiasm, Esperia is enjoying herself, while you are trying to just stay alive and hit her with a Cleaver which has a pitiful reach. It feels very much like Esperia is playing the game, and your the victim of it, rather than the inverse.
Range of Abilities: Esperia is just as deadly in hand to hand combat as she is with the Archonfire Powers at her command, she also mixed up the typical boss fight with a 'avoid falliong debris' minigame that is both hard and intense-- challenging. This versatility of her different powers makes the player feel very challenged.
She's not even trying to kill you: Esperia has no intent of killing Pep, nor defeating the player, as neither are any use to her dead, she seeks to break the Cat's spirits, and scare the player shitless. But you know she could be doing so much more if she wanted to just outright kill the character, but that's never been her goal, as a result, the player fears her because she's playing nice.
All in all, I'm very happy at just how powerfully she comes across. There's a succubus in a not-rpg for ya, lel.
As for me, I've begun deep dev on Perseverance: Full Clearance!
I expect, it's release is not as distant as was once feared.