"Weak demons"??

Guys, is it really impossible to use your brains and think logically? The strategy for using Battle Standard of Purity (BSOP) + Sign looks approximately like this: two or three units are placed in battle (depending on the development of the racial skill), and the hero casts Sign on the enemy unit (it only moves 50% along the scale). Then, "Raise Dead" is used (if there is "Tent" or "Regeneration," it's even easier), and the enemy is killed in passing (the Sign is moved as needed). With "Ballista," all that's required is a certain amount of accuracy, nothing more.

Added 1 minute ago
P.S. A couple of years ago, I posted a demonstration replay where, thanks to BSOP and Sign, a hero of level 10 killed about 15 Phoenixes.