Can't progress past Blood of Arlathan "Defend the Area"

I need help because I've experienced a game breaking bug that refuses to allow me to progress any further into the game. 

I arrived at the gate where I fought the first wave of venatori and my other companions are trying to open the gate. However, when I get the tag line to "Defend the Area" against incoming venatori, the second wave never spawns and I've been trying to fix this for four days now. I've tried absolutely everything that I've seen others do online: I've lowered the graphics, put into window mode, restarted the quest from the very beginning and even went further back, restarted from auto save, changed up the order of going to the gate to the scaffolding, waited out the fight for as long as possible, etc, etc. 

Please, any useful advice on what to do, I was really enjoying this game and I've never experienced a bug like this before.