I agree that 1 Minotaur cannot defeat 1 Black Dragon.
BUT this does not follow from your reasoning)).
The Minotaur blocks any NON-magical attack, and it doesn't matter if it blocks the counterattack after its own attack, blocks the first attack against it per turn, or 10. Therefore, a Minotaur with 100% block is invulnerable to ordinary, non-magical units)).
Well, yes. Theoretically, the Minotaur's victory over the Black Dragon is possible, but very unlikely in practice. Although I have had cases where the Minotaur deflected up to 6 attacks in a row! but unfortunately, it was not mine:(
Added 3 minutes ago
In my opinion, vampires are most useful in the early stages, then their usefulness decreases. And if the Death Knights are fighting against a tactician and do not have their own, then even 50 extra vampires, in addition to the main ones, will not save them. Although you can get out of any situation, but still...:)
Well, if a Minotaur with 100% physical attack block will constantly defend and not attack, then this will continue for a long time. Example: 1 Minotaur and 1 Black Dragon. The Minotaur cannot attack and block an attack simultaneously. and as soon as its attack ends, it will receive a fiery breath from the Black Dragon. And the Minotaur will definitely not avoid death.
Regarding the health of vampires, I agree. But if its HP is increased to 100, it will be stronger than a Champion. And a creature of level 3 cannot be stronger than level 4. All this leads to the fact that the Champion is weak.