I will generally go for top 45 degree with a bounce card on the flash or a stofen (bounce card in large room, stofen in small). This seems to be the most fool proof way, especially when there’s more than one person in the group. It also requires less flash power than blasting backwards. Shooting outdoors a bounce card can be really useful to give just a touch of light to the subjects and it gives a catch light albeit not a great one.
I just find the times I’m using on camera flash most of my photos will have more than one person in it. I’m not sure about having an assistant with a reflector either as it would just be easier having him or her carry a speed light in an umbrella or light softbox like a gami light.
Direct flash has its advantages, my old canon does 1/400 flash sync speed with a manual flash and combine that with 10 fps you get a touch of strobe light to your subjects if shooting sports for example. Just don’t piss them off too much or cause epileptic fits 🙂