I mean lithobolos and ballista are underpowered, but oxybeles and mainly scorpion are seriously overpowered. Scorpion have a excellent attack and range, better than ballista against buildings, and of course it has against infantry ans cavalry. It makes ballista a no used unit because its function is better asumed by scorpion. I mean scorpion must have less range (90 m) and less attack against buildings, being a infrantry sniper, but with less rate of fire, because it's actually a machine gun: five scorpions can destroy a whole army. Ballista and lithobolos must have 50% more of attack against buildings and about 100m range, but being no usable against infantry, with a poor attack against it.