I have the Rubicon Express 3.5" lift, which sits at about 4.5" true height, with just a transfer case drop. Absolutely no driveline vibrations on my rig.
Some people get the death wobble, some people don't. I don't know why, but that's just the way it is. If it were me, I'd try the drop first, and if you get the wobble, go for the drive shaft and slip yolk eliminator.