Disagree, not everybody has access to a pelta. But whatever, that isn't the point. Slingers are basic, that's why they're in the first age. Since they're on the first age, they can't be too strong and neither too fast (talking about moving speed), else they become OP, for they're ranged. They must also have low armor, so that the buildings themselves are a good counter against them. But later on, they become useless, unless they can be massed. And they can't be massed when their cost of stone, a resource needed for your defenses, is so high, their defense so low and their attack being nerfed. It's not that they can't be massed, it's that those who mass them would be dumb if they did so, a fort would do better with no food cost. That's what i think.