Discord is awesome! Very easy to use, easy to connect with other player in the clan and organize events and raids. Also easy to sneak in other clan rooms and negotiate switch and maybe even snoop a little. I really like it a lot and I was always wondering why it is not used more in business setting or for coordination in teams, because it could totally do that and it is ligher solution then slack or god forbid hipcha…
Yeah honestly I don't see why it couldn't replace Slack, it is a very similar product but I feel like by marketing it primarily to gamers they are positioning themselves in a far less profitable market than Slack is.
Services like Ventrilo, Teamspeak etc required a lot of setup/ self hosting and were only really strong for voice. Skype didn't organise well around how people game.
When I come back to WoW a few years ago a lot of people were trying to run groups on Skype which was a horrible experience of adding randoms and joining group calls, in additional to all the other downsides of Skype. Discord is a perfect replacement for that.