Maulerfiends move 12" and ignore terrain. They'll be in people's faces just as quick as the talons or the prince. I don't believe I need cultists, they're not good, and easy to kill in small, objective holding groups. 6-8 vehicles? I don't agree with needing a ton of vehicles. It comes down to needing to play test the list to trim the fat and perfect what I bring.
I really hadn't thought of flyers, actually. I have no idea what to use to take them down.
Interesting about the champion, I'll have to check that out further.