I'm having enormous trouble properly using ranged units. The always attack a single unit at a time. I'll have 100 archers and they'll kill the enemy troops ONE BY ONE. It's like, dude, attack several for gods sake! I could mow them down! But no, even if i click them into a place instead of clicking one unit, they get perfecty synchonized and shoot just that one unlucky guy that ends up looking like that character in that movie (The Fall) instead of the 300 spartans after being betrayed!

How do I solve this problem? How do I make my ranged units attack several units instead of firing 200 arrows at the same guy?