If you watched the gameplay provide on the YouTube link, you'll see some examples of flawed gameplay. For example: the last 10-15 minutes are easily dominated by covenant forces as the elites just hug the shield wall and wait to kill the Spartans as soon as they rear their heads.
I wasn't a fan of this gameplay so I changed some stuff. To heavily discourage spawn killing right at the shield wall, I deleted many decoration items to put a highway right above the entrance where Spartans will...
So once Elites died and simply spawned on their teammates still in the city... (most likely with the assassin loadout) and the spawn killing commenced....