Just wanted to share 2 things that can make Omnigul easier, that a lot of people don't seem to know.
First, remember that an armor piercing sniper can shoot through the Steel door on the upper level of the room before Omnigul. This allows you to kill the pesky Knights that spawn above the doorway and drive you crazy, without having to stick your head out and have it removed by boomer fire.
Second, the heavy ammo glitch works everywhere, not just in the crystal room at Crota. Follow the same procedure you use to prep (emptying ammo) for Crota at the door you have to open before Omnigul. Open the door and rather than sprinting forward, just walk lazily and empty your pistol before the Thralls spawn. You can make a truly ridiculous amount of heavy ammo with all of the Thralls that spawn before the hill climb, and it will all sit there for the rest of the strike. It makes the Omnigul fight FAR more enjoyable.