In the current beta 0.86, the only way to cure heroes is with a restoration potion that you can get by doing certain quests.  There have been a number of suggestions of other ways to repair the damage, including special buildings that will cure heroes, and the option to cure an injury when the hero levels up.  Hopefully we'll see what the developers have in mind in the next few betas.

Infirmary would be a more logical choice for injury healing. I forgot to put it in my mod, but I will put it on the list for the next update. I already made the potion available from the Apothecary.

In the preview I saw, you can't farm gildar from items. In my mod, you can't get much gildar from items either. I priced it at about 800 Gildar because it takes away all injuries. With the way I have the late game economy set up, that would be a large investment for any player. But let's be honest, heroes are the best weapon in the game. It is worth it to revive one from retirement. I will likely add a spell in at some point that costs 800 mana to do the same thing. 

In my mod you have to really worry about scouting early on. The monsters are very aggressive and quite numerous. It is nice because it means there are fewer enemy factions going about, killing every champion. I also increased the number of champions. The devs only added them without accounting for how many would be killed. I am trying to assume that you only get the ones within 12 tiles of your start.