I'm considering attempting MM3 or World of Xeen with a small party, 2 or 3 characters, for an interesting replay option. Can anyone who has tried this give advice on what classes/party makeup would be good for this?

I recommend paladin(or cleric)/archer(or sorcerer)/ninja(or robber) so you get the important mage and cleric spells and thieving.

You absolutely need a robber or ninja in WoX to enter Necropolis and locations related to it.
In MM3 you can do without, just leave a few chests unopened in the beginning and go to the location where you can buy all skills for 100,000 gp early, you could add a ranger(or druid) instead for access to druid only spells (there are no druid only spells in WoX).