I should have been more clear, sorry, I need to see which bandit you're talking about (there are many) and what TES4Edit shows their inventory as in the bashed patch. Otherwise it's impossible to say for certain whether the iron armor is normal or not. It wouldn't be out of place for a marauder, but a genuine bandit? That's questionable.
Well, I couldn't find the exact bandit in question, but I remembered enough about his location, race, etc to know where to get a general idea to find someone like him in TES4Edit. And checking the TIE.esp file, it seems like it's normal in T.I.E. for Bandit Ringleaders to have a full set of Iron or even Steel Armor.
So I guess there's nothing unusual. Just that T.I.E. introduces various bandits that sometimes wear heavy armor. Very different from the norm, but I guess that's what makes T.I.E. so awesome.
Sorry for wasting your time there, if I did.