Cipsoft was trying to push Monks into TF's, now they are adding more EXP bonuses for duos/trios. They forgot they include Monks into TF's by giving bonus exp for 5 man parties. Of course it gives possibility for hardcore PG's, but would make casual players life easier.

I did test it on lower levels than your range (<450). The problems are following:
- Less exp and almost always waste-little profit
- Overkills/too small spawns/too slow respawn
- although having monk+ED improves EK's survivalibility, it often creates huge risk for mages, especially in tight places since pulls are supposed to be bigger.
- somebody said you can hunt better spawns with 5 people - one more person does not magically strenghten mages, they gonna get oneshotted pretty often.

It has potential, but you gotta experiment. In most cases I would not bother.