Also, sending big numbers of creatures isn't also a tactic per se. You aren't really saying anything about how do they fight.
I disagree. As the old axiom goes, "Quantity has a quality all its own." The Soviet Red Army in Western Europe outnumbered NATO forces 3 or 4 to 1 normally, and could be expected to achieve 6 to 1 or greater at the point of effort. Mass is also a principle of war, where you concentrate overwhelming offensive power at the place and time of the attack. Overwhelming your enemy with greater numbers allows you to concentrate superior firepower on multiple targets at once, while forcing your enemy to either weaken their attack by spreading their firepower on multiple targets, or only attacking one target at a time.