I am genuinely curious though as to how Void is more useful for the Gatekeeper. The waves are non-stop, you can't spam that super or your void nade, having good Void weapons are far more useful IMO because of this. Being a Sunbro that can carry two nades that can drop shields on a Praetorian and allow for a self rez scenario while wielding a great Void secondary and heavy (or even primary if you have Aetheon AR) just feels more valuable to me. Let me know if I'm missing something here.
Ok, Gatekeepers.
DPS down the fist Gatekeeper from the hallway with 6 ice breakers and then run to the first portal on the left. This will despawn all of the hobgoblins and open the first portal.
Two people go in and take the Gatekeeper to almost no health. It's really useful here for a Bladedancer to stay behind inside the portal and stealth and wait. The second person leaves the portal and the whole team goes to the other portal to let the Praetorian take the first sync plate.
Doing this will stop all Praetorians from spawning on the right side, but A LOT of goblins will spawn. Voidbomb is great here, although I put two blind bubbles at each spawn point to make this trivial.
Once the right portal is active, two people go in, take down the Gatekeeper and run out. While this is happening the other three that opened the right side run back, take out the oracle that will spawn over the portal, kill the Praetorian and open the portal so the person inside can kill the first Gatekeeper and come out.
Then you all move to the middle and defend.
At ANY of these points, Voidbomb and Void grenade faaaar outweighs a self-res.
And please, if you haven't cleared heroic. I know Sunbro is fine for normal...