Tactics for playing as/against Barbarians.

However, it's best to play as a Knight hero with dragons against Barbarians. Of course, the hero should be well-developed. Once, in a game with many Knight and Barbarian castles, I bought only 5 armies – one wolf for gathering resources and 4 red birds. With these 4 birds, I defeated a total of about 50 Cyclops, plus hundreds of Trolls, without a single loss. Unfortunately, the Knight army suffers heavy losses, as does the Barbarian army.
Basically, against well-developed Barbarians with good heroes, you need to have an even better hero, or even two. Sometimes you can ambush a companion and prevent their powerful hero from escaping, and then eliminate them by sacrificing one less important hero.