About the Roman Army in a nutshell

[Garvanko]

I think you're confusing "light Infantry," and "Skirmisher" The Hastati were intended to attack first, wear the enemy down and soften them up for the Princepae. They weren't inteded to have much staying power, which is why I term them "light" the fact that they were generally less well armoured just re-inforces the point.

Hastati fought as the leading edge of the early roman legion's manipular formation. It they really were light infantry wouldn't they have been given some kind of role on the flanks? The stats for Hastati and Principes are pretty even - its just that historically, the older more experienced soldiers were Principes. Greater experience and slightly better armour gave them slightly better stats, but not that much better.

Both were clearly heavy infantry.