I completely agree, this mechanic seems way too harsh and forces you into a very cautious style of play. I think there should definetely be a penatly but it should be much lighter.

Of the options suggested above, option A would be my favourite. That or make the heal injury potions available from any city (or allow a structure to be built that provides them, such as an alchemists) and make them fairly pricey.

We had immortal champions, and it was absolute shit. It did not work. All you needed to do was equip them and autoresolve every fight until you won.

I like the current injury system, but I think there should be more ways to get rid of injuries. For example, a level 4 spell that removes a random injury, costs 250 mana, researchable.

before the injury trait there was 2 options: 1. heroes DIED when they died in battle or 2. they didn't die as long as you had won the battle. 

1. Nobody liked death. Whats the point of investing large amounts of time in a hero only to have him die in some random battle? Doesn't work.

2. This was almost as bad. With no repercussion for sloppy play heroes became unstoppable powerhouses way too fast. There was no need for regular units at all, just a stack of undying heroes.

The injury mechanic forces you to be careful with heroes. They are high risk/reward units  that in later levels and with equipment can become more powerful than any other regular unit but require you to think about using them especially in big battles.When you commit your top level heroes you   are throwing down more power but have more skin in the game as it were.

The injury mechanic is a great balancing tool and the players screamed for something like it in earlier stages of the beta. It forces you to be cautious with them at lower levels as you should be. When a regular unit dies in combat they don't come back, they are dead. When a hero dies, you don't lose your investment in time and money but you get a penalty for careless play. As you should.

Don't tie injury removal to mana either, that just means people with lots of nodes will have ravening unkillable hero armies again. You shouldn't be able to buy your way out of penalties. The level-up removal.....that has some merit, it means that if you got your hero killed, his injury can go away eventually. Its not quick or easy to remove the injury but possible.

That all being said, the AI needs some work on how it uses its heroes. It gets them killed a LOT and never retires or even bothers to accompany them with units often. 

There  IS   a partial remedy for this issue, built into  v0.90 !      In my current game, one of the Magic Items that I was able to pick up, from a minor Quest, was called: "Restoration Potion" .  It was described as restoring a hero's health (up to 100 hit points!) immediately,  AND  " removing all injuries champions have from escaping combat".  Sure enough, I passed it along to one of my heros who had suffered a "permanent" injury as a resulf of a deadly, losing, battle, and it  DID  remove his "permanent" injury !  

I thought (and think) that this was a great solution, for this issue!  We could still have an honest arguement about whether this is the best way to go; and/or also, how common or rare this particular magic item should be in the game.  However, it is one way to deal with this issue ... and I must say that I am delighted with it !     

These were quest results, correct?  Which means they can't be researched, and may not turn up in a given game, at least for the questing human player, leaving a champion you've spent a lot of time working up, never recovering. Perhaps if these could be researched as a high level magic tech.

The problem with really punishing the player for being "careless" is that of course they don't have to take it.  They'll either reload before the battle, or grumble and put the game away, possibly for good.  It's one thing for a player to get the result of a careless decision and accept this, and another for the player to perceive themselves as treated unfairly.  It's like the old game mechanic for dealing with pickpocketing, per Baldur's Gate: every person in town suddenly turns hostile.  What does the player do?  They reload.  The solution fails if it causes the player to erase the event.

As usual, Glazunov1, you make some good points; and have provided a thoughtful commentary.  ( In fact, I am really glad that you started this Discussion Thread; because I think it is an interesting - and occasionally, dismaying, - issue! )

You are correct, that I secured the   Restoration Potion   by completing a simple quest; so it is not researchable, or a guaranteed solution.   It is part of the  Wonderful World of Randomness!   Still, the whole game of FE is so much about randomness, that I still find it to be an agreeable outcome.  Better a random chance, than no chance at all ...

As to " ... really punishing the player for being "careless" ... " , I guess it depends on how you look at it.  IMO, most injuries aren't Game-Breakers -- they are just part of the overall experience.  And, as far as that goes, I (personally) have no problem with reloading a saved game.  ( On the other hand, I know there are some people who hate to do this -- out of Principle. )  The thing is: none of these circumstances/outcomes would cause me to go so far as to put the game away for good.  In fairness, once one gets beyond those of us, who are relatively hardcore 4X or RPG game players, there is another group of more casual players, who may feel more strongly about this ...

In any event, I would be happy to see the discussion continue ...