Personally i use it to coordinate weekly Warshade Wednesdays, and keep up with Mastermind Mondays on Indomitable. And just generally shoot the shit in General.
TBH Discord is the default these days for groups of people in games to coordinate and talk to one another. If you arent in there you are missing out on things that you might be interested in simply because thats the only place its being discussed.
Id say Discord sits in the middle between forums and instant messaging.