In search of the Rune Sphere.

Good day. I downloaded the map because I really liked the first one; it was a great battle between humans and dwarves. And I encountered a problem: I'm reading reviews, and everyone seems to be completing it without too much difficulty. What's the secret? I started on Veteran difficulty, and Vittorio emerged from the dungeon, and a chaotic battle began above. I had very few troops (there were no losses in the dungeon), and while there were no thanes in the dwarf squads yet, it was manageable; the berserk griffins landed wherever they could, but far from the enemies, and the ballista fire was effective. But when the thanes appeared, the question became: how do I kill them? If I don't manage to capture the tent, does that mean I have to restart?