After playing the demo about 40 hours, I starting to feel like that crossbows are too early and do not fit the age 3. In age 3 we still have Spartans/Spears/Shortswords, the cavalry and siege equipment just got unlocked and you have already crossbows.
Better pacing would be :
Starting with Slinger -> Archers -> Crossbows
OR
Early bowmen -> Archers -> Crossbows
OR
Place them to Age 4.