If you want this game to be more balanced and to give people a chance to defend there city from stronger players the bonus from hero's command/might/magic/stamina should be lowered to 10%. 30% to all stats is so insane it is equivelant to almost two troop levels.
10% all stats is still a huge bonus and would be way more balanced, If it stays at 30% weaker players will not even bother to defend their cities from a stronger player because they will not even injure a troop let alone kill them. If it was lowered to 10% atleast the person has a chance of doing some damage even though he will lose the fight and take hospital. This would make it worthwhile to defend your cities from stronger attackers rather then just sitting on the sidelane and watching them while you can't do anything.