I disagree with you. Not on a personal level but on a game mechanics level and a historical level.
I'll explain, please don't feel that this is an attack on you, since I think this game realistically representation of nobles back then.
Peasants starve, malnutrition and disease walked hand-in-hand. Nobles, as you may have already surmised, were the last people to go hungry. Barons, then Counts, Dukes, Kings and Emperors, in that order.
So dying from a disease due to a weakened immune system due to malnutrition, was rare for the nobility add to this, the fact that they actually had access to medical professionals, who did study the Classics in Greek and in Latin. You and me, we'd get to eat mud pies and tree bark jerky, we would probably not see 50.

But the Count, the Duke and the King... well, "it's good to be rich" is a saying for a reason.
Next, the game has to adjust for the mores of modern life. You can't have 13 year olds getting married, pregnant and having kids because... well, you know. So they had to extend everyone's lifespan by 3 years.
So while I agree on your most basic stipulations, I think you need to discern between the lifespan of a noble vs. a peasant, first.