IMPROVEMENTS TO DUEL
To further improve the rules governing duels, we have adjusted the Power requirement for initiating duels. At the same time, the side that initiates a duel must deploy enough units to reach a certain threshold of Power before the battle starts. If the threshold is not met when the countdown timer is over, it is considered that the player who initiated the duel is defeated.
you need to add one more rule:
The defender needs to be required to be bound to a minimum treshold of deployed power also - or lose the duel. the rule that all heroes are injured who did not take part in the fight needs to be removed - as it is utter nonsense. the one hour "cant do any PvP" is harsh enough. I would even go as far and say remove it, it was a bad idea to start with.
on top you should add a +- x castle levels requirement to the duel rules. for example: your own castle level +-4 levels. Means a player with level 20 castle level can only attack players with a castle level 16-24. this rule could be added to castle attacks also, but I think here it isnt really necessar - maybe even counterproductive ... for pvp it is needed to guarantee a fair game.
as you want to install a minimum power that needs to be deployed, I want to hint you towards a power maximum deployment cap (dependant on castle level) to prohibit people attacking with all gold troops in duels - this should only apply to duels not to sieges. for sieges you absolutely need all the gold troops you can get to be successfull.