Well one suggestion could be to create three different instances of the same event. In either the description or the title, specificy that this event sign up is for Warriors, Mages, etc.
That way you can see how many you have of each signed up.
Just a suggestion.
Another feature I would like to add to this is putting a cap on the number of players that can sign up period.. EQ2 has a raid cap of 24 players. I would love to have it tell people that the raid is full once we hit 24, or even put it at 26 for a buffer incase a couple people don't show up..
I agree that this would be a very handy tool =)