I am pleased to see the increase in cost for ancient times, as I tend to fly through that era. I will let you about the rest once I reach those eras
One thing I wanted to say about balance was the healer unit, why is it so strong? When healers become available, they have the same strength as the strongest units (hunters, stone ax, stone spears) and as a result the AI tends to build a lot of them. You see AI stacks with between 20-30% as healers. To me this seems excessive, healers are a useful unit, but how many would an army need? Also they are being used in a military role rather than a healing one which seems wrong to me, I feel they should be weaker, maybe reduced in strength to 2 and with a penalty against archery and melee units.