Here's an example of a level 5 wizard that wouldn't toast a bunch of level 2s:
Level 5 Wizard's Spell Slots
4/4/3/2
0: Detect Magic, Prestidigitation, Mage Hand, Detect Poison
1: Magic Missle, Charm Person, Shield, Expeditious Retreat
2: Mirror Image, See Invisibility, Fog Cloud
3: Haste, Big Nasty Dragon Spell
Scrolls: Gaseous Form and Dispell Magic
Wand of Magic Missles, Bracers of Armor +1, Cloak of Resistance
Potion of Cure Moderate and Cure Serious
Yes, he's heavy on the defensive spells, but logicaly, why SHOULD he have Fireball memorized in a city? Most of the big evocation spells he could use are a big no-no in a city if you want to avoid being hunted down by the guard, and aren't really that effective in the day to day routine. Also, unless he was expecting company that he wanted to toast, he'd probably be most concerned with avoiding confrontation. He's still only got 22 hp, which goes by QUICK.
He would probably be very, very irrate, and wanting to track down later at his leisure those that crossed him, however.
Well, that's a level 5 example, which doesn't look like it can do much. If you want, boost him a bit higher and give him a wand of Summon Monster II or something. Just avoid the massive direct damage spells, and you should be fine. Remember that Magic Missle can start to hurt if you add too many levels though (unless it's from a wand, which should be a measly 1d4+1)