So you definitely want some synergy in your Raiders and characters.
In my Raiders, I run this set up:
Drazhar + 2x5 Incubi--- He buffs them, and the small squads are able to hit multiple units. I usually hang this one back and counter charge hard with it.
Archon + 1x5 Incubi + 1x5 Wracks--- I try to run this boat alongside Drazhar to get both buffs from Drazhar and the Archon. In addition, the Wracks usually stay inside, flame or get out on an objective. They also are my ablative wounds should the Raider get blown up.
Succubus + 2x5 Wracks--- I play this Raider aggressively and position it in a way to pressure my opponent. Should it get blown up the Succubus is there to protect the Wracks.
If I had a squad of 10 or less wyches I would put the Succubus in with them, but I run 1x15 Wych squad right now.