Defensive Swarm Hosts?

In Heart of the Swarm, Swarm Hosts were introduced to kind of play the same Lurker did in Starcraft I. However, the Lurker could be used pretty well both offensively and defensively on multiplayer games.

In HotS however, it seems Swarm Hosts are used more as a 'siege' unit to siege defenses. Does it have a viable role as a defensive unit, ie used to defense an expansion or base, or should it be considered an offensive unit only when playing multiplayer games against live opponents?