It will also probably help if you also make public test threads/posts for getting people to join a test game at gateway, channel, time (mention timezone), map. If you're able to organize it this way maybe some wc3c members will meet up on irc or at channel on bnet.
All at least changing the message of the day on irc that today we are going to play and test the map "Planet Buster Heroes" at 16pm for example. I'm not sure only Vex can or you also have access to it. But at least better than nothing.
Bnet players is unfortunately notorious leavers and you never get a game without leavers except trusted clan mates in a clan, which only rarely leaves for real life events and also explain that they are going, instead of just leaving without saying a word.