They have a bit of duality. Deep strike the S6/7 guns to threaten rear armour or deploy on the table and ping away with a 60" twin-linked S10 lance shot. Fortune their saves to keep them alive in the backfield makes that S10 shot pretty durable, and it can move and shoot, as the unit is Relentless. Deep striking will kill them, however - T3 and a 4+ just isn't anywhere near enough to survive in that role. They might be able to Hit and Run, but they'll either be shot down or whatever assaults them will kill them before they get to run away.