I would go for gladiator, assassin, priest and lich, for the practical reason that you cannot get the experience for the priest and lich promotion quests without actually promoting a character to that rank.Hints and Tips
The priest is the only character apart from the ranger who can use the best bow in the game, Everstrike. That compensates to some extent for his poor ranged weapons skill. The lich, on the other hand, has a fair ability (master) with thrown weapons, so give him the throwing axe Tillhygge when you find it, and don't waste skill points increasing his bow ability. Give the other artifact thrown weapon, the dagger Trolleri, to the assassin, of course.
Arm the assassin with two daggers as soon as he has the skill to use two.
ALWAYS and I really do mean always, keep a backup saved position from before you enter the dialogue asking for a promotion. It's very easy to cock this up, and in this game, you only get one chance to get your characters promoted. Check if it's "taken" by pressing Z after ending the dialogue - for all cases except the lich, it should say at the head of the character summary what the character is a candidate for. If you mess it up, the only way of correcting it is to edit your savegame. (The lich candidature appears after you've taken a particular action, nobody actually gives it to you.)
