I don't see how it's any different than currently asking for experience in the fight. The only difference is you lose that infinitesimal chance the group will say "ok, let's just go" after entering and seeing the "new player" message. If someone wants to make a farm group, that's their choice. They shouldn't be forced to enter an instance and find that some people don't meet the requirements, and have to go back out and repost their party finder.