There are three main boss fights that require you to be able to communicate with your fireteam I am only mentioning two. You need call outs for a room right or left to get safe in at the right time or you wipe. There are tv monitors that pop up left and right on the same fight that need to be shot at call outs help. Other parts require call outs to be in the right place to take down the shield of the boss if you are not in place it is pretty much a wipe. So if you can't talk to your fireteam it would be pretty much impossible to complete. So you really need a mic to complete this raid lots of communication between members of the fireteam. Hope that helps a little bit more than yes you need a mic.