i have developed a successful wizard character. the key is in the death knight. make him your tank. there may be a point where you have the death knight in front for a while, but you can choose the option to make both characters aggressive or not depending on how you want to work it.
key things to remember:
tactics: pause the game with the spacebar. pay attention to the life bar levels. you can use potions in pause mode which become effective immediately after pause is lifted. be sure to select the potion list for the character that needs it.
tactics: the aggressive option for the fighting stance of the 2nd character, whoever is that character. if you have the death knight as your tank, and as the leader, make sure you set the primary combat skill on the hero to his spell. he won't enter melee but will cast from a distance. make sure you have enough mana & health potions.
spells: initially, they may seem weak, but in time you can get them rather powerful. a rather nice combo that i came up with initially was to add 1 point to each element for the skill wizard > elemental attack > focussed > missile when you have the points available. this ensures that you damage your enemy regardless of what elemental resistances they might have.
spells: healing for the hero character at least. this way the DK can use the potions.
skills: i discovered in time that identify while useful, became unnecessary as one can come up with enough gold if they collect everything they come across, to afford merchant identification. i did have it initially to level 2 or 3 but unlearned the skill eventually once i was equipped to my satisfaction, and put the points into more useful skills for survival reasons.
skills: summoning doll upgrades are good once you get the summoning doll, to boost it a few levels and buff it some. keep in mind these cannot be unlearned. i know, i tried. Larian rightly realized that this would quickly become spoiler like in terms of this particular skill group. summoning dolls add an additional defender for your mage character. while their travel radius is limited, pausing the game and then bringing them out into play during combat is useful. make sure to select all so that they will obey commands as well.
equipment: charmed items are a good thing to pursue. while i had the benefit of the ungodly arrow gold mine before patch 1.45, making it easy for me to get charms for the items with charm slots, you are able to find some useful charms. also keep an eye out for certain boosts you find in act 1 and act 2. in act one there is a secret raanar temple below a statue of the damned one. there is a book there you want the hero character to read. it will boost your health by approx 60 points. in act 2, when you are summoned for the crystal fragment quest at the abbey by the necromancer, look for a holy grail. having the hero character use this will boost his magic by about 60 or so points.
potions: use any permanent potions you come across for the hero.
