Too many people have said it but none have managed to state it properly. Here is how the game is played - you have a party of four people and you generally have the following roles - cannon fodder (warrior), beatstick (warrior), dead weight (rogues), God (mages). As for the party itself, you need:
- a dead weight - to open locks/disable traps. Since these can specialise in ranged or melee, maybe ranged is better, because they tend to survive longer in a fight. However, I've had several experiences with a melee dead weight that manages to use some of the more powerful abilities in the beginning and as such turns (very) briefly into a cannon fodder and a beatstick. Don't take more than one, it's a waste of space.
- beatstick - give them a weapon or two and give them the boring job - grind down the HP of the enemies. God should just stand back and do the actual work - buff/debuff and own the fight.
- cannon fodder - they are there to absorb damage, obviously. They can even turn into HP batteries for God later on (Blood Mages). You definitely need one to take the heat. Also try to keep him alive for a bit but he's not essential for the entire fight. Also, don't play a cannon fodder. Beatsticks and God should focus on finishing the battle, even the dead weight can be a more contributing factor there.
- God - one, preferably you, and maybe two to split the responsibility and double the effectiveness. The responsibility of God is to win. Pure and simple.
There are specialisations for God, that (unless those of lesser classes) actually matter - they are the following:
- Shapeshifter - useless. Worse than the dead weight.
- Spirit Healer - not too bad but one of your party members will already have that. It is still possible to pick it if you are God.
- Blood Mage - you have to get it. Period. You (or one of the other Gods) will absolutely troll the battlefield - the first ability, Blood Magic, will make you cast from HP. Not impressive but can give you extra juice to win a fight. The second ability, Blood Sacrifice, takes HP from those party members that don't need it (i.e., not Gods) and gives it to you. The third is Blood Wound. THIS IS WHY YOU PICKED A BLOOD MAGE. Is that clear? No? OK, here, let me rephrase: DOT and immobilisation for everyone in a huge AOE and neither is broken if the targets are attacked afterwards. Only works on enemies with blood, which means most of them. Oh and there is also Blood Control - pick an enemy and make it an ally. Or deal massive damage if it fails (although there was a bug that didn't deal the damage, IIRC).
- Arcane Warrior - if you want to take over the job of beatsticks and cannon fodder and be better at it. It does take some planning to use effectively but an Arcane Warrior Blood Mage (yes, you can have two specialisations) is probably the most powerful being you'll encounter. And you'll be that being if you're playing God.
As for what you play, you can take the role of the dead weight - it's actually fun and if you're doing the job, chances are you'll be able to considerably outdo the other dead weights. To the point where you're useful to the fight. It makes the whole party more effective because you don't need to drag a true dead weight with you.