The first Guardbots do very little damage and are easily killed with a single Bazooka shot each.
Later in the game, Guardbots are considerably more dangerous. They move quickly, have long-range projectile attacks as well as melee attacks, and have a lot of HP and defense. Alchemy is best against them, as their physical defense is high.
The Guardbot gives a large amount of experience, but the player can only encounter it a finite number of times and so cannot level grind against them.