Watch this video of a very messed up "Mass Attack" scenario for these officers. When I get a chance I will do a write-up on tactics and concepts which they did not use in order to get through this situation.
What could these officers have done differently?
I have been in several very large "flash mobs" that didn't care too much for anyone who resembled me.
When you see an obviously aggressive person in a group and you need to make contact - NEVER split up. They surrounded them, do not do this. You guys need to stick together, even if its just two of you. Form a triangle if possible, contact officer does the work, backup pulls people to the side and away if possible. One guy fights, backup officers cover him or take measures to remove the threat off the officer.
stay off the ground - this is a death sentence for someone as you saw in the video. We have weapons, they might have weapons, going to the ground and ground fighting in this type of scenario only leads to deadly force.
Learn how to do a basic arm drag from the standing position. This will give you the ability to "pass" a person from on side to another and move them away from you. This also gives you the ability to walk around people and the group.
Stay mobile, move out to the edge of where people/groups are and stay facing the group with no one on your back other than your backup.
If you are going to strike, it needs to be extremely violent. "Violence of Action" is something that needs to be displayed here. Go low and knock them down if possible - hip toss those that get a grip on you, if you go down with them, your backup should be there to remove them off you and help you get up.
It was extremely frustrating to watch the officers split up, take one on one fights (police do not fight fair for a reason) and then leave an officer on the ground fighting a guy one on one, what happened? BG went for his gun and deadly force had to be used. This was inevitable in my experience.
What should the average person do in a mass attack situation? Sometimes the best option is simply to run away if you cannot fight. Going to the ground will almost certainly mean you will be kicked in the head, which is, of course about the worst situation you can find yourself in. If you have to run, do so and if any of them follow you then you may be at a lesser disadvantage since it may be you vs a few BG's rather than a whole group.