A simpler way would be to use one variable, and a few self switches.
For the three characters to talk to...Add what they say and then add...
+1 to the variable
Turn self switch on...
Make another event page that requires that self switch on so they don't repeat their speech.
Do the same for other 2 characters.
For fourth character...
Make 2 event pages, the first is blank so he/she won't appear on the map.
Second page, make it require that the variable be equal to 3.
Add whatever else speech on the second page...
Second page will be autorun
First page can be anything besides autorun/parellel event
If it's too complicated, I could make a demo
(Just noticed you asked Garlyle to simplify...oops, oh well)