Rogue/Wizards are ok because they get a TON of skill points. You can go two routes with this one.
1. Go with a Elf and pump DEX and INT. This will give you loads of skill points and a decent AB and spells. If you go 20 rogue/20 wizard you can be a jack of all trades. Go Rogue 30/Wiz 10 to be a rogue with some powers to supplement your abilities (invisability spells etc)
2. Never really liked Fighter/Wizards as you need to many feats to be able to cast in Armour.
3. Monk/Clerics are great as the Cleric spells boost your AB and they both benifit from a High Wizdom. Pump your Wisdom and DEX for these builds and get some decent Gloves.
4. See 2.
5. I wouldn't bother with this build because unless you keep all the classes close together you will be hit with a 20% XP penality.
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