Well, I would tell him not to get too comfortable with landspeeders, the Coven supplement only has 2 sources of AV both of which are expensive, Talos w/HWB or HL, or a Talos beating directly on a vehicle for that matter and a Raider. Landspeeders will die to everything else rather easily. So gauging landspeeder success against this book isn't the greatest of barometers.
Simply put the supp just doesn't have the AV punch out of the box and will always struggle with it unless you invest heavily into more raiders with your wrack squads or bring a few Talos along.