My WM party is really lame in random battles. If I want to level up some new characters, what's the best way to do it? I heard something about pasarans becoming easy to grind on the 20-something floor.
Sheep. Oh wait, wrong game.
If you want to RNG exploit you can grind Scylla. Just pick the first quest (the one with the Wildling), take only one party member, and just escape. He will instant-kill her for you. Free XP! See this if you are having problems.
Otherwise... bosses give lots of XP. Just get a sleeper for the 14 day respawn.