If you're on a pinch, you can use keyboard macros to communicate.
I have the Logitech G15 with 6 (x3 profiles) dedicated macro keys. Some ideas:
G1 = "Stay together! Please don't run around by yourself."
G2 = "TANK! Get out to the open area!"
G3 = "I'm pinned. HELP!"
G4 = "Keep moving forward together!"
G5 = "Jump down together in 3 second!"
G6 = "RUN FOR IT!"
You can be a lot more creative
