I really like the way the game is going. As you know siege workshop units are too strong in general in most land games. I dont feel that the problem is the health of the units or their damage. The problem comes when people mass siege. You have so many catapults and bombards that nothing can get close enough to kill them and the only way to counter siege is with siege.
We can stop the massing problem be making seige units cost 8 or 10 population each. The whole point of them is that you are not supposed to have a lot of them. If somebody wants to make 10 catapults and that costs them 100 population, they will have to give up eco or army for it and keep the siege numbers down.
This may also give siege more of a power spike in the mid game when people arent worried about maxing their supply.