No. I don't agree with separate rules for the AI.

The AI should be taught to avoid the big dragon until it can beat it. Rules should be the same - the AI should just play better. It will probably get "perks" anyway, at least let death be the one equalizer, whether it's saying dead or taking a negative trait and/or other penalties. As far as reloading, that's up to the player. I don't think a game system should be structured around "the player can just reload". The player can also mod .xml files, should the system be around that?

Game systems should take into account only what's in-game actions and results, imo. If the player wants to reload every time they lose, so be it, but the base game system shouldn't take reloading into account.

I think this topic is quite important.

First, giving (serious) injuries to heroes can help balancing the game which -after a few games now- seems to favour heroes.

Secondly, injuries are fun and add a nice touch of customization to heroes. . A nice way to remember your miscalculations in tactical combat.

As a fallen emperor, I will definitely use my 'beyond repair heroes' to cast the paragon spell or something like that (once the UI let' us choose someone else than the sovereig as the caster), and let them be old crones to defend the cities for when their adventurers day are long gone.

This is something Dominions 3 does very right IMHO. Weak heroes or now useless heroes become researcher in a castle. Also, holding some statistics about how many foes heroes have slain would be cool !

Most traits you get from dying aren't even that bad. It won't break a champion to have a few scars. 

I had the exact same experience today- my champion died, but since we won there were no negative effects. I don't mind but it seems like I'm cheating.

Another vote for some consequence for killed heroes in won battles  - wounds or time needed to be spent recovering