Ok I don't know if this is overpowered or not, but I've found it to be a ridiculously good strategy with the current beta.
Pick Paladin, get Mysteria worship as soon as you can, then use your healing during fights to level up piety, healing is so cheap that it will level up very quickly. Now spend all your piety on the 'magic' boon which gives you extra mana points at the cost of extra monster magic resist. The trick to this strategy is the fact that you're attacking monsters with your sword so there's no drawback to taking this boon over and over, as long as you remember to cast heal or another spell every couple of swings the god won't get angry.
Take on the hardest monsters you can, and use healing liberally. You'll quickly see a snowball effect happen, more heals -> more piety -> magic boon -> higher mana pool -> more heals and by the time you're level 6 or so you'll be taking on level 8's without any problem due to the sheer amount of healing you can do. By the end of the game your mana pool will be around 30 and you'll usually be level 9 or 10 by the time you take on the final boss.
The boss itself is easy because you'll have so many heals, mana pots are ridiculously good with this strategy because they're based off your total mana pool.
I haven't decided on the best race for this build but I'm leaning towards dwarf or gnome. If you find and destroy a few glyphs before getting worship then gnome is probably better since mana pots are so damn good, but if you get worship first then it will anger the gods to do so, so you're better off going with dwarf.
For preparations, the only one you really need is Scout: Altar, but good weapons and stuff like the mana burn immunity helm will make this strategy even better.