Generally, I almost never take old-grade units, except perhaps with the Unicorn Bow. Maybe it’s actually more effective against low-level enemies, but I doubt it’s significantly so. However, it’s clear who to take against archers and high-level enemies, as they pose the greatest threat in terms of damage output. Theoretically, masters should be even better against fast creatures that rush to your troops on the first turn. First, masters will push them back with their attack value, and second, they will receive the same direct-hit bonus as the blue archers, since the enemy will be close.