If you have Occult Impaction, you can go to the Turtle Dungeon lvl 2 and occult the turtles with a strong weapon. AGI build is useful, so you don't get hit.
Or if you like Combos, you can also try Lighthalzen Biolab lvl 1 & 2, but to be more effective in there, I would suggest to get at least a Fire and an Ice Fist in addition to your Berserk.
Another place that comes into my mind is Kokomo Beach (cmd_fild02), with the Seals and Mobsters. I remember training my 98 Combo Monk there as well. ^^
