Dagg covers those questions and he has a huge clearance punt that is second to none should the flow or change of the game plan allow it. Yes Ben Smith is better at full back but drastic measures need drastic actions.
Dagg in my opinion is essential esp with clearance and catching the classic highball in his own 22 without panicking. Gotta remember that without Cruden there's a slight re-adjustment in defensive play with directional kicking on the back foot.
Having a huge punt is about the only thing he has though, and you can't mention Dagg and defense in the same sentence as they do not go hand in hand