A unit of Camillan Hastati will cut a unit Peltastai to pieces (suffering many loses for sure), so that should be true for Imperial Legions as well. Wall fights have their own rules.

Amongst the Iberi units, there are some that look like nothing but have AP swords. I had really started to fear these guys and prefer to encounter any stack of Carthagian heavy spearmen with Sacred Band cavalry than facing one of these units Iberi holding a gate, or simillar situations with them.