And what is a good party setup?
I'm kinda struggling to get anything done above novice level dungeons, I use warrior or paladin up front, cleric second, rogue/mage/noble third and ranger last.
My favourite is probably 1st-Warrior/Paladin/Alchemist; 2nd-(whatever); 3rd-Cleric/Maid; 4th-Ranger/whatever
Warrior is good up front. Cleric I like in the third rank as they can still bash from there if they need to, and it turns on their mass heal. Paladin is good in first or second rank, depending on what you need them to do. If you need their healing, they need to be in the second rank, if they're just there to do damage, then first. Ranger is good in the back and can do both damage, debuffing and emergency healing. Mages I've found are a bit odd, as they can do a lot of alpha damage, but also seem to have a lot of focus on DoTs. Early on, DoTs are probably going to be able to do more consistent damage.
Second rank is probably the biggest 'flex' slot, I think, particularly for the Rogue and Noble who can move back and forth as needed easily. Maid can also do most of her support stuff from there. A more 'battle' cleric can also do good here with Shield of Faith, but as mentioned, you lose her mass heal ability. A higher level mage with Flameblast is also a great single-target nuker. Particularly if you can get Loral with a Crown of Intelligence.
One strategy I like is taking a warrior or other tanky starting class and making them an Alchemist and giving them the shotgun, and putting them in the front rank. They can be very durable there and do a good amount of damage too.
Prisoners make great frontliners to just be damage sponges as well, so it might be worth getting a girl cursed with that class early on just to protect the others. Cowgirl can be a good tanky type as well and depending on how you want to use her, can be good offensively or as a backup healer. Pet can be good in any rank, Bark can do good damage with a muzzle from the back ranks and her melee attacks and counter tokens make her decent towards the front too. Need to be wary of her counter attacks moving her out of the back if that's where you want her.
In general, having a girl who can cure DoTs (Ranger, Maid, Cleric, Pet to a lesser extent) can be vital in some fights. Having ways to do AoE attacks or DoTs, or ideally, both (One of the Meguca as a ranger, for example, or a Maid with the pink duster and Dust Storm) is also handy. Having ways to remove enemy buffing tokens like a maid or ranger can really smooth over some fights like with goblins. Of course, healing is important too, and Clerics make probably the best there, but having a backup maid, ranger or cowgirl doesn't hurt either.
Also, I believe the team of a Warrior, Rogue, Cleric and Mage gives a special bonus. I think there's others, but can't recall any off the top of my head.