Those two pets barely give any incentive to a player to summon them since WoD, especially Voidwalker, because at that point utility as well as incentive that they brought along with them to play with those two pets were completely gone, this is especially the case with Voidwalker more so than Succubus, I will elaborate on both.
Voidwalker atm is a pet that has its use in leveling and soloing environment only. Utility it offers in any PvP environment is non existent at all with the removal of disarms from the game. What I mean is that they have removed basically the only active/utility spell the pet has and forgot to replace it with another. Now I think that Voidwalker should be given back its sacrifice spell back where you sacrifice him in order to get shield that absorbs certain amount of dmg for 15s or 20s, I don't exactly remember how much that shield lasted... It could be as well in iteration of Cataclysm where that "Sacrifice" spell had 1 minute cd and didn't kill your pet off, they can as well incorporate it with a 1 minute cd and killing off your pet...
Succubus atm no one in any environment uses because of 30secs cd on Seduction which is a lot... Even when seduction wasn't on cd that pet had only being used in bg environments in situation 1v2, where opponents didn't have their trinkets and 1v2 could be pulled off.
Would especially like to see Voidwalker's sacrifice spell back, because I think that it looked very cool and had as well very good fantasy behind it that fits that of a voidwalker...
I really would like to see them reverse the 'pet for a spec' decision. Pointless, regressive, and nonsensicle. We shouldn't be taking a DPS hit for utility. I don't like "but no other spec..." As an argument but here I think it's valid.
i think the voidwalker is okay for the most part. if you have bad gear, it can hold aggro well enough. if you have a high ilvl, it probably won't, but everything is dying very quickly anyway
as for succubus i'm totally with everyone else, it feels absolutely useless
I take the Supremacy talent so I use the Void Lord for soloing/ questing because it allows me to ignore a lot of stuff and just go straight for the quest objective and it holds threat really well.
I've never used the Succubus, though I have used Shivarra...but only because I absolutely hate the beholder pet model. Would much rather have the Felhound, but with the introduction of the talent that lets you summon a Doomguard I never use the Felhound either.
I only PvE, so any PvP utility is completely useless to me.