Change Barbarian Rage -> Barbarian Rage (3x/day) due to clear unbalanced for the moment. Will add fighter as suggestion though will still discuss it in the following.
I’ll admit I inspired myself from playing a Barbarian and complain about dying from Rage (although the feat couldn’t be used when unconscious), which is again pretty strong. Thinking back on it, I wouldn’t call the Barbarian I’m playing a tank, even though he has 60hp at level 4. Why? Because he doesn’t go above 20 AC without being warded by another character. He doesn’t have points in parry nor does he have the intelligence for expertise. Is he a bad character? Not at all, but he’s not a tank- he’s a flanker.
So I suppose it’s more of a building choice? To focus more on hp and Rage time rather than balancing into INT and trade Improved Parry and Expertise for Rage feats, or multi-class (side note: illiteracy seems to me like a feat which encourage Barbarians to multi-class)? So perhaps there should be options for the non-casters in a low-magic settling without 14+ INT builds?
Compared to a Fighter who is in a way perfect for multi-classing because it grants proficiencies, feats and BAB. Pure fighters are rare since the class didn’t had access to unique abilities until the introduction of class feats along with charisma feats. Wisdom fighter is also a thing, but only with wisdom archery.
These are more things I leave for discussion and more changes. As for the amount healed, since the con modifier is already implied in Second Wind, Mathias adding the lvl to it would be too small? Also to be discussed.