I've played through shackled city a few times, there are a LOT of traps. You need someone able to deal with them, and you need to be able to start doing that at level 1 or else run the very real risk of a TPK. Also, you'll really want, possibly need a caster, if there was some class that synergized rogue/scout with cleric or druid I'd recommend that. Since there isn't the first choice I'd recommend for this is, Gnome Beguiler going Shadowcraft Mage, has really good skills, but lacks the Wizard's power. Spell Thief, Wizard going Unseen Seer, finishing in Arcane Trickster gives a good amount of sneak attack, you lose only one level of casting and a nice amount of class benefits, including a good amount of skills from level 6 onward. Lastly a Beguiler Wizard going Ultimate Magus for if you want to be GOD, although GOD doesn't usually do stupid things like scout for traps someone needs to, and at latter levels you get to fling around all sorts of metamagic for free.