Good point about the loot not matching the units value. I'm changing the loot system so it's based off unit cost and scales with levels. Should be out in the next patch.
I think maybe for expensive units that cost Crowns like Dragons and Heroes we might consider making it so that they don't die at all, but instead just go unconscious and lose half their levels. That way there is still a loss but not a huge (possibly financial) loss.
Other more easily acquired units we could still look at adding a revive/resurrect option with cost based on Strength and Level.