Hitting a level 10 npc will require a lot of troops and some great effort but can be done i suggest that you hit mainly level 5 npcs because after that you will lose troops but the best way to attack a level 10 npc and WIN is
archery and logistics at least at level 8 and your rally point must be of level 10
scout the city until you get a low hero under 10 is best (the lower the better)
you can scout time and time again and diffrent heros will come up but when you hit a low hero stop scouting
then send with your best attack hero
92k archers, 2k ballisters, 2k transports, 3k warriors, and 3k workers
with this you will win but you will lose troops mainly all of the workers and warriors but not much archers no ballisters and transports
you can also use corset and war horn to help aid in attacking with few loses
i have used these all and have worked