I never played that game.
To make a long story short, the succubae in that game can be parasites that eat the souls of humans and when they are ruled over by evil incubus kings most do. Some even do it because they enjoy the thrill of the hunt and a minor few are actually addicted to eating human souls. In the Last Sovereign game, even after peace is achieved between humans and succubae, there are still clans of succubae that hold to the old evil ways and hunt down men and kill them to consume their souls. Some of these evil succubae even target the men who are with other succubae in committed relationships as they derive extreme pleasure from destroying the happiness of their sisters in an effort to corrupt them back to the dark side.
When left to their own devices, the succubae in Sierra Lee's world actually choose to take husbands from the males of all races. They have found that they can actually live far better only drinking the life force from male semen on a daily basis rather than being forced to go for long periods between meals by hunting and capturing men. They can also sustain themselves with regular food but they still need men from time to time.
If I had to point to the big difference between that game world and yours is that in yours succubae are created, where as in the world of The Last Sovereign they are the result of a union between a mortal man and a succubus. Mortal men have to get a succubus pregnant for them to produce offspring.
I guess maybe that wouldn't be as bad for you, as the succubae have a good reason for why they don't prey upon humans like they do in your games.