I see the first cutscene of mercenaries running over the bridge and the turrets firing on them, but as soon as I kill them the screen will turn black. I can still hear whatever ambient noise there is in Dantooine, but no cutscene plays. There is one wave of mercenaries and that is it.
Okay, as I was writing this I loaded up the save again and it somehow worked again. I've tried saving and reloading before and it did not help, but this time I had a save from after the first attack when my screen went black since I was still able to access the menus. I loaded that save first, and it was still broken but the screen was no longer black and I had control of my character. The cutscene still wasn't triggering, so I loaded a different save from right before I talk to Zherron and start the battle, and the battle went smoothly and I finished the Dantooine story. Interesting thing to note, I had two Azkuls on the other side of the bridge giving orders.
So problem solved, I guess? I have no idea if my summary of what happened will help at all, but I figured I would throw it in here anyway.
edit: should mention on my successful attempt, I was NOT in windowed mode, I use Windows 8, I let Zherron decide who defends what side, both Azkuls were gone after completing the battle, and everything seems normal.