We decided to require Discord after receiving numerous complaints from players in the League that their opponents who weren't on Discord were difficult to get in contact with. Real-time communication is much easier for scheduling purposes than asynchronous messaging.
Of course it is. But you don't get real-time communication just by installing Discord. You get it from installing Discord and being online most of the time, which means either spending a lot of time with the PC/laptop where you can install Discord or having a portable device in your pocket which supports Discord. Neither of which is true for me.
So, to get to the real case. I work on my employer's PC and Discord is blocked there (haven't checked, but they block Gmail, Facebook and all similar things so I guess Discord too). My mobile phone is not a smartphone and there is no Discord app for it. When I'm home and not sleeping (which is approx 1-2 hours in the morning and anything from 8 to 1 hour in the evening, depending if I go somewhere after work or not) I get online regularly, but only checking every 20-30 minutes unless I am doing something which requires sitting at the computer, so no real time communication. With this lifestyle I have played in multiple online tournaments which required scheduling (mostly Netrunner), including some where most of my opponents were right at the end of the world from my point of view (Europe vs Australia) - I communicated with them via pm, we found good time to play, I sometimes needed to reorganize my day a bit and the game happened. Do you think this availability is enough to take part in the Dominion League?