Bob couldn't be weak if he had all his magic skills maxed out. My Arthur had around 800 health (somewhere between 770-80). So, he definitely wouldn't be defeated in the first round. And in general, it's hard to take him down, considering he also has an army, artifacts, his spells (both summoning spells and curses/blessings), and, if necessary, the Amulet of Life.
It's a real pleasure for me. And he didn't need any protection. But I repeat, this is the limit, the maximum.

Even with 1000 health, what about the number of monster units at that point? Surely 2000 damage won't be dealt! And if you attack a large group of Djinns or Sorceresses without at least some magic resistance, the mage won't survive to the second round...

Added after 4 minutes
By the way, in my opinion, it's much more effective if the heroes' magic skills are divided, that is, the mage has 3-4 main magic skills + combat, and the combat hero has, for example, combat + tactics, 1-2 magic skills (one Life magic, and the second to complement it), and nobility or scouting in the 5th skill. The difference is small... This is a very effective combination, any Castle becomes the strongest then, whether it's Death or War... or almost any