Various mods by zahar0z

you can upgrade the black guards to level four, give them abilities focused on defense (like wall of shields, great shield, and others), and with seven-day cooldowns, it works out.

I would explain the situation with Dark Messiah by saying that Saref attacked the guards one by one, but their strength lies in discipline and combat formations + Saref is a skilled wizard's apprentice, while the guards are recruited from different social classes.