I think when you battle multiple enemies, it shouldn't be random, you should battle like Team 7, Team 10, Sound Genin, Akatsuki teams [Itachi and Kisame; Deidara and Sasori/Tobi], Shodai and Nidaime, The three sannin, etc.
It shouldn't be like, Naruto, Gaara, Gai, Zabuza, and Orochimaru. This would most likely put alot of pressure on the server, but it would make alot more sense.
also, I haven't noticed, but do you get more experience depending on how many enemies you fight? if not you should.