You'd be the one shouting... thus you'd make the rules to get what you want. Sure not all of the groups happen but a lot of them do at least on my server they do since I see the same people who shouted for Briareus now shouting for Sobek.
You know what, I've tried that a bunch of times. Getting people by shouting isn't as easy as you think. I, nor the first one or two people I persuade want to wait an hour or more just to form a group to maybe kill an NM once or twice out of the 30 times needed.

WoE is substantially faster, and that's why it's available as an alternative.