This is all true except your last point. The ogre spawn actually depends on the number of rotations crota has done. The ogres will spawn after he rotates back to middle from one of the sides. That's why you especially want to kill the first sword bearer as fast as possible.
English
-
So far the ogres only spawn for my group if crota goes left. If he goes right we get a swordbearer. Start battle first swordbearer is there. Killed it and hit crota blah blah. Crota goes right another swordbearer. Crota comes back to center and nothing. Crota goes left we get the ogres.