Nice game, one problem
It's a really nice game with some humor in it. But there's one little thing I get annoyed about. I don't think it's the game problem though... There are times after I got a new medal, the medal icons just won't unlock, even refreshing the page wouldn't work (sometimes). It's really not a bad game.
Now for those who plan to go against some boss monster at a relatively lower level, I recommend you to...
1) Get the [Buff] All spells. To me, magic is worse than melee unless the melee is directed to your mages & healers. Start out with Shell/Harden All depending on the type of enemy you're facing. I made Reuben the fastest healer to make this possible. Healing Water for higher players is good. Then again, always buff your characters before attacking, Haste to me is not really necessary.
2) Try beating every Bahumots you find. Summoning them is very useful as it grants all buffs (except Haste) along with Regen. Very useful indeed.
3) Play Zombie Defense if you have to. I could get high quality slime food by winning Expert level to feed to my slime for some good stuff.
4) I hate to say this but you're gonna have to GRIND a bit. This is especially to unlock the side quests that grant you bonus AP. The side quests unlocks after every 3 levels (6 for one type).
5) Don't try going against any boss monster if you're not at least 2-3 levels below its level. It's dangerous unless you can come up with some strategy to beat it.