This is a problem that I've found with 0 A.D. --Real quick preface is that I'm not the best RTS player, but I think I'm pretty good, but there are some bad balances with both 0 A.D.'s AI and the game itself
I have not played it, but I've heard stories about people playing competitive World of Warcraft where they had to send EXACTLY two soldiers to collect gold, Exactly two to build and then train 10 grunts and blitz, because that's what everyone else did.
0 A.D. seems like this. OK, there are some ways in the game where you shouldn't be able to everything. (If I just pick flowers in minecraft I'm going to get myself killed really quickly) but 0 A.D. should not have a specific "way" to win. OK, you do need to shoot for wood and meat in the first level, but I should be able to do it in different ways. I should be rewarded by putting a few soldiers on metal and stone at the beginning. I shouldn't have to pour everything I've got into soldiers, because if I don't, I get mobbed by 50 spearmen 10 minutes unto the game. Building walls would counteract the spearmen, but I'd need the resources and builders for that, and that requires more soldiers and I can't get all of that done.
How can this be addressed? Firstly, by rewarding players for branching out. My suggestion was to change the resources required by the resource gathering upgrades, so that the player, if he put people on metal, would be rewarded by making his wood soldiers get upgraded, yes you could ignore that, but now its a choice. Just getting wood and metal might allow me to get lower costs, but If I can wide balance it, my late game time will be easier.
Then in regard to rams. @Vantha's been doing more research, but in ancient times a siege ram would be murdered by a handful of men without protection. It should destroy buildings, but it should only be protected from arrows. Everything else should cut right through it.