Evoker. Abuse firecrackers before combat to group enemies while stealthed, fire an empowered minolettas concussive missile into the group = dead enemies. As soon as my evoker got his level four spells (minolettas concussive missiles) I quite literally breezed through every player-initiated encounter on POTD difficulty. Evoker damage with empowered spells is just absurd! Red triple skull mobs fell at my feet! I think, perhaps, that there's some strange beneficial interaction between evokers, the empower ability, and any spell with minoletta in the name. Because no other empowered spell ever had the same effectiveness while empowered. With the one exception being, delayed fireball, because casting it from stealth doesn't initiate combat which means you will still be able to use an additional empowered spell once combat begins.
Admittedly the first few levels are tough. They didn't have to be but I went with a min max evoker build (18m/3c/17d/17p/19i/4r) which made me fodder for ranged enemies and put me at a major disadvantage during early game-initiated fights because the game ignores your group order and puts the main character front and center, directly beside your enemies. But again, as soon as you get your level four spells, you dominate. Also, it's very beneficial to dump your skill points into metaphysics because there's this shield called "Cadhu Scalth" which when upgraded provides % reduced damage that scales based on your metaphysics stat. It's obtainable in the Old city/old city ruins which are accessible by going to the gullet in neketaka and taking the lift down. It requires two shells to open and is gated behind a boss, although you could sneak by him, possibly. Once I got that shield my evoker became very, very durable. Pair that with "Nemnoks Cloak" and you have a dangerously powerful character who is also nigh unkillable.
One last thing, and this tip isn't just for wizards, but I would highly advise actively looking for and equipping items one-use-per-rest summoning items, these are a huge help. The summons can deal tons of damage, especially when paired with certain pets (animancy cat available in sacred stair in neketaka) and they take the heat off your party, letting you focus solely on damage. Arguably one of the best summons can be obtained really early on by salvaging an area on a small area just north of the starting island. At least I think it was north. But this item is a little different because it's a necklace, still, it's amazing.