The Incubi, after the new FAQ are the strongest and faster unit in war 40k.
Actually, they got a power fist with I 6, AS 3+ and if you put the archon with shadowfield in this squad, so is not easy to destroy them.
If you try to put the Incubi in the raider and in the same time you move toward the middle of the battle the wyches with lelith, Your enemy,of course, will choose your wyches as target and not the Incubi.
P.S. in the second turn, The incubi are in the middle of the battlefield and that's it.