So I noticed the other day that Scourges are pretty awesome at providing cover saves to Raiders, along with forcing the enemy to choose between an easy kill point/vehicle threat, and a Raider full of something nasty. (Obviously you can fire easily over or through the Scourge wings) Another thing I've wondered about is using turbo boosting Jetbikes to screen the aforementioned transports AND take a 3+ cover saves themselves.
Obviously these tactics are for a couple things only, and that's getting some measure of protection on sparse tables or providing more options when trying to get through an unobstructed enemy killing zone.