One of the dungeons you guys have upcoming for you ( at least for those of you at the level 10+ range ) is Aria Reservoir.
Shit is pretty fucking difficult on your lonesome, and is where i got stuck at before i took a hiatus from WO. Right off the bat i'm going to say we will need a Thief for sure. Possibly a wizard, as the living coin enemies don't seem to be hurt much from melee.
Also, expect more riddles and puzzles, and even more depth. If you thought Golden Dragon Ruins was bad, well this is worse.
As for the Thief's use, we will need one with good Decoy skills. The room leading to the FINAL final battle is pretty small, and is filled with Killer Coins and a Bullspawn. The room has two doors. See where i'm going with this? Alone you won't make it at all, for even if you kill the bullspawn, the coins will drive you fucking crazy trying to open the other door, meanwhile another bullspawn shows up and kills your ass as you try and escape out the other one.