There's a deaf group that plays so it's certainly doable! The only time I really felt like it was an issue was trying to beat Skolas before TTK came out. Dancing, waving, or pointing to indicate when you needed to pass the green crud just didn't cut it for me. The Raids aren't as big of an issue as long as the mute player knows what they are doing and is extremely observant. For King's Fall, it may be difficult if you couldn't let your team know when you're torn between dimensions and have gotten the relic. Otherwise, I don't think it's an issue. If you are playing with LFG's or people that don't already know what to do and how to work as a team, then it might be more of an exercise in patience. When your mic/headset is turned off, do you mix the audio so you can still hear the team?