Tactics for the Stronghold.

Hi everyone! I need an expert's opinion. Yesterday, I encountered a rather unfair situation. My friend was playing as Neela from the Tower (defense), and I was playing as Crag Hack (attack). Our levels were roughly equal, plus or minus 2 levels. I think I was level 21. My skills at the time of the battle were 21, 13, 3, 3. Neela's skills were 13, 11, 13, 12. I had a significant advantage in troops: 10 angels, 62 Rocs, 26 Cyclops, 172 Orcs, 60 Ogres, 220 Wolves, and 360 Goblins. My friend had 7 Titans, 55 Nagas, 26 Djinns, 60 Mages, 115 Golems, and 560 Gremlins. My friend surrounds his archers with melee units. The game begins. I go first and give everyone a speed boost. I attack a Naga first with an Angel, then with a Roc, and then I don't remember, maybe with 2 more units. In the end, I didn't kill anyone by the end of the round. I was practically killed by the Nagas alone. I'm seeing this for the first time. Usually, the Citadel deals insane damage on the first strike. But this time, something went wrong. I got the feeling that I'm not an expert in attack, and my attack isn't 10 points higher than his hero's defense. It felt like I was attacking with a regular hero against a defense expert who is 10 levels higher than me. Today, I calculated the strength ratio using the tables. It turned out that I should have been dealing about 20% more damage than if our skills were equal (attack equals his defense). Can anyone tell me why, with such good skills, I was dealing such pathetic damage?