Well, I believe there's alot of misconception about steel in the Classical era. Most people say that steel was invented in the 18th century however this is untrue. In the 18th century people started to produce Steel in industrial quantities. Steel is a junction of iron and carbon so, not very hard to discover.
Now steel is believed to be around long before that. I don't know if Roman armor or weapons were steel I never read anything regarding that subject. But, finelly tempered iron can be tough as hell. And, as Watchman pointed, Longbow is way over rated. The best bow around is the composite bow eastern style. And, plate armor was always at advantage regarding chain. You said that from experience mail is more flexible. Can you assure us that the LS shirt you used was built on Roman standards? For you to have a Clue, a 16th century fully incased warrior had less weight on his shoulders than a British WWI soldier with full gear. So, they had plenty mobility as you can see. Now, LS in general I saw some schematics in a book I own and only 2 layers in fact overlap exept in the shoulders where you can have as much as 4 and the unshielded arm would be a much valued target as it would be the most xposed part of the body.


Cheers...