Followers need to be able to self heal and heal you if in danger automatically, who else feels this way?Also does the armor they wear have any effect on there defense or ability to take hits doesn't seem like it, your armor should also help the follower as much as it does you.

They already self heal. Your character self heals.

Companions use the exact same armor system the player does.

They just dont have access to all the perks the player does, I know they have some, based on what class they are, but not all.