I just went back and noticed this old thread:
http://forums.civfanatics.com/showthread.php?t=516098
Never noticed it at the time because I was off in my own world
Must say that I'm definitely on the side that Carthage is too powerful. To me, it's not even a close call. First off, their unique ability of getting free harbors in every city might be the most powerful unique ability in the game, although I can't think of every civs unique abilities at the moment. It's at least in the top 5 (of over 40 of them). Greece's unique ability of basically getting to ally with every city state in the game might be the most powerful.
So, given that they have such a powerful unique ability, you'd expect that their other unique units/buildings would be rather tame. Nope! Not the case! The Cothon is also one of the strongest unique buildings in the game. I read Thal's arguments that when you get a free luxury resource, then trade it to an opponent, then you gain happiness and they gain happiness. Here's the fallacy in that:
Normally, I play on large map sizes with 10 players (me and 9 AIs). Say I have 5 cities and 5 copies of that unique luxury. I get one of them, then trade 4 of them away. I gain a net of 20 happiness. Opponents get 20 happiness, right? Wrong. In total they get 20 happiness, but it's distributed among 5 different civs while I get to hoard all of it. That's in addition to any normal luxury resources you'd be getting. That's a net +16 happiness over each of me neighbors. In addition, I like to trade resources with weaker civs, so this means that I'm giving +4 happiness to 5 weaker civs while I'm gaining +16 happiness from their luxuries. Not even close to balanced. In my opinion, I think we should look at re-working the Cothon, or at least delaying it. In my mod, I have Sailing as a early classical era tech with the Cothon available then, so that's a move in the right direction.
So, the Cothon disables the need for Carthage to worry about happiness so they can expand at will. Next, you add the free harbors on top of that. That means an automatic +1 happiness per city if you get the Liberty policy for +1 happiness from city connections. Then, they get free gold from city connections IMMEDIATELY. Then, they can forgo building roads, so that means that road maintenance is essentially free. Plus since the workers aren't building roads, they are free to concentrate on other tasks, like mines and farms which causes their cities to be even more productive. This is over the top by a mile.
Then, we're not done yet! They have a unique unit (which seems okay). Plus, they get a free starting warrior and starting bireme. You can use the bireme to knock out barb camps, so here comes even more gold. CHA-CHING! Plus, who needs to build an army to protect your workers. Your cities are coastal. Use that Bireme to knock out any barbarians in the area. Get a quick settler from liberty. Send him out unprotected because the Bireme has cleared the way. Quick easy 2nd city....no problem.
With all that, this civilization is beyond over the top. Then, hey why not? Let's add a free 2nd tier tech just to throw a cherry on top! How anyone cannot see that this is ridiculous is beyond me. It's out of control. No wonder when I run into AI civs that are Carthage who started on a separate continent from me it turns into a really boring game really fast. I recently was playing a game as Ethiopia. Carthage started on the opposite continent. I didn't find out they were there until Astronomy. By the time that I found them, they had expanded like crazy. In the Industrial era they dotted the entire map with cities. They were raking in around 600 gold per turn while I was getting 150-200 gold per turn, and I'm typically very good at building a strong economy. That's just the typical experience with Carthage. Once it happened again and again I decided that I'd had enough and it was time to nerf Carthage. BTW that last experience happened after I had already removed their free Sailing tech.
Take the Sailing tech away merely as a start. They need more than that. The free harbors combined with the Cothon is over the top. One of them needs to go. You can't give them free gold and free happiness. I'd prefer to keep the Cothon as at least that's an active trait as opposed to the passive free harbors.
A civs uniques should be balanced across their abilities/buildings/improvements/units/etc. The Cothon is one of the most powerful unique buildings in the game. Maybe not the most, but it's top tier and could be #1. Their unique unit is rather mediocre and middle of the pack. Maybe even bottom half for the unit. So, just assessing the building and the unit, they're above average (compared to other civs unique buildings/units excluding abilities). Logic points to them having a below average unique ability to balance them out. Not happening though. They get a free bireme, free sailing tech, and automatic city connections letting them rake in the gold. Most powerful unique ability in the game (or top 5 most powerful). This is why they are beyond overpowered.
To balance them, you need a nerf to their unique ability (harbors) or their really powerful building (Cothon). Eliminating Sailing is merely the beginning. Also, the Bireme needs to go. In my mod, I've replaced the Bireme with a Trireme (which I have on the same tech as Biremes BTW and it's early classical). Starting Triremes are less powerful than starting Biremes. You can explore coasts with them but you can't attack barbarians with them unless its a ship. I've given free starting Triremes to a handful of civilizations, but only a free starting Bireme to 1 civilization (Indonesia). They get one because their unique ability involves civilians being able to embark on turn 1 so that they can settle islands. They need some way to protect their civilian settler when trying to found a 2nd city. Indonesia has a really strong unique ability, but to balance it out their unique unit (Kris Swordsman) is fairly weak and their unique building (Candi) is very weak. Carthage has no such balance.
So, right now in my mod they have free harbors, the Cothon, a starting Trireme, and African Forest Elephants, plus the ability to cross mountains. No free sailing and no warrior so at least they can't get goody huts. It's a start. Also, the Cothon comes in the early classical era, so at least they can't use that to expand right away, so a move in the right direction. I still feel like they are too powerful even with all that. The combination of the Cothon with the harbors is just too much, even without Sailing. The Trireme isn't all that much and neither is the unique unit. Maybe shifting that Cothon to do something else would balance them by weakening that building. Maybe if you had it do the same thing but be a replacement for the Seaport instead of the Lighthouse? Anything that affects the early game tends to snowball, so early advantages are really strong. A Cothon building as a replacement for a Seaport would be a below average unique building. I think that might balance them better overall since they have such a powerful unique ability. Just an idea and my thoughts on the matter.