It seems that you're using an outdated browser. Some things may not work as they should (or don't work at all).
We suggest you upgrade newer and better browser like: Chrome, Firefox, Internet Explorer or Opera

I've been doing alright so far with:

Druid, Paladin, Mage, Rogue, Cleric

They seem like they can take just about any generic setup of an appropriate level, but if anything extra specialized is out there, it could get harder. I've been with this setup for a while, and it gets hard to think about changing it.

Rogue does the most repeatable damage per turn, but Mage and Druid can stack DoTs on targets one at a time. Rogue seems like a pretty powerful boss killer, but I'd probably be fine swapping that out for Hunter if I had one. Concussion is the only one-point wonder, but the resistance debuff could potentially matter. I don't know much about late-game monsters or whether they have 80% all resists or anything dumb like that. If I had a party with a bard and all physical damage, I could see resistance lowering mattering a lot. Berserker might be an acceptable replacement, but it does not begin unlocked.

Paladin could probably be swapped out with any tank. This class slows the game down, where higher-damage lifesteal tank hybrids could speed things up again, at some risk.

Druid brings a strong DoT and a party mana restore. Heal over time is also a handy release valve for some fights.

Mage has a DoT, and Meteor is sort of ok if you want to wipe out seven weak units for the lulz. Mostly Fireball and the passive skill are worth points, and the stun is a good one-pointer.

Cleric doesn't feel all that necessary, and could be swapped out. It's not that hard to take on enemies a couple levels higher, so the heals aren't a huge deal. Smite's self-heal goes to waste pretty often. Weakening raises too many questions - does it get outscaled? What are the mechanics? Will bosses be immune? Usually I just assume everything's immune to this sort of thing, so I don't like to bother with it. Anyway, Paladin+Cleric is most likely overkill, where a Cleric supporting a DPS/tank hybrid might make more sense and play faster. Paladin+Cleric is super reliable with extra safety, though, and Druid puts it over the top.