I was getting random classes to level 10 in three minutes in a "PL party" where people took turns massacring the puks and willowisps in Nanawa while everyone shot the breeze. things slowed down at lvl 30, to about 1000 exp a minute.

If there's a lot of enemies, and lvl 50's can stomp them, then its got the potential for exploitation.

Be prepared for contract killers too. "U gib gil, I lebel U"