I suggest to give the title for those last ones who survive for each class.
Therefore each class has 3 winners and they get what you listed(title+insane, chaos, and high)
Disable all those curse magic + pepsi and return, dispel should be banned as well to prevent any awkward moment such as priest vs priest at the end.
also buff everyone before it starts.
AND
2 Round -> Get the most killing streak during given time( same place, same prizes, and same rule)
I think that'll be a good event since it will encourage players to be more aggressive and not becoming the lovemusic mode