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?

Swarm hosts can work quite well defensively if the enemy engages in a medium sized choke. E.g. The average choke to a natural. However, it is easy for the enemy to bypass this. If the enemy drops in the main or on top of the swarm hosts, it will take too long to reroute the locusts. By the time the next wave of locusts is in position, the enemy will have had tonnes of time to inflict undefended damage.

Sure, if the enemy is on the defensive when your swarm hosts are sieging an expansion, the enemy can also drop on top of your swarm hosts. The big difference here is that if the enemy commits a large portion of his army to drop on the swarm hosts, the current wave of locusts will batter down the expansion.

So the difference is that when swarm hosts are sieging, the current wave of locusts are forcing the enemy to a certain position so that he can defend. When swarm hosts are defending, the current wave of locusts can be easily ignored by the enemy.

It is really in my opinion the Zerg equivalent of the Terran's Siege Tank. It works well in both roles offensive and defensive. You actually use it in the campaign at one point to turtle off and hold off a attack. Then at other times go on the offensive. So it seems like it was definitely designed to do both roles.

The unit fires off locusts, so they must have a way to path to your enemy. So you can not have it fire down from a cliff (unlike Siege tanks). They need a "walkable" path to get to your enemy. With the vision your creep spread usually gives you it gives you quite a decent amount of vision for your siege unit defending.