I think that he Swarm Host is simply too risk free to use. It really needs to be designed as artillery (with living ammo), rather than a little unit making factory.
Make the swarm host tethered to the locusts. Make it that they once again have to burrow in order to fire, but if they unborrow, their cosponsoring locusts die. This means that much like tanks, they have to commit to the area in order to sustain the attack.
Heck, even a disruptor cannot move while firing a nova.
If it’s to remain a factory, where they can make locusts and don’t have to commit to the area, the locusts need to cost minerals. There needs to be SOME cost/commitment to the actual attack. It’s amazing that they not only can launch and run, but are also pretty quick.
Even with a nerfed Nydus, it’s never going to feel fair that the locusts can attack something, while the SHs have already left and are on the other side of the map, safe and sound. It’s boring to watch, as well… as there’s nothing for the attacker to lose. Their units were free. No real battle is happening, no commitment to the fight.