Wow. Talk about a mechanical disaster. Honestly, this is almost a bug report and I'm not even sure of any good ways to fix it.
So the gate functions exactly like the gate to the Ziggurat. Which is fine when there aren't Nightrisers on the other side, and when you don't need to react with running. But because it's a convo script used to flee, there IS no running. There are two guards down there, sure, but they are utterly useless because it's just a jump via convo script.
So, I suggest this be changed to a two gate system with the outermost swinging open and able to be closed and locked via a floor switch. Also, guardsman goblins in the central area to help.
Have goblins exist in the area just beyond the door. They'd be Elite Goblin Warriors who are there to protect the Gobsquat against Nightrisers. Have them imitate the more civilized colony by calling themselves members of the Pallid Mask. Remove the Nightriser spawns from that area, and if you get in trouble from Nightrisers nearby you can run to those goblins and they'd attack the undead.
This keeps the gate the same. Alternatively, it could work as Garem suggested, with the aforementioned goblin NPC's standing between the two main gates.
Having been recently raped by this transition, it definitely needs a rework. I would be fine with just no Riser spawns in that area. But the idea of Goblin guards powerful enough to kill the Risers isn't a bad idea, either.