I have now played about a dozen games using the DA mode. At first, I thought I was going to really like the mode. It sure made playing as a warmonger rather easy. Basil+DA is a steamroller to victory. However, once I stopped playing as a hyper-aggressive civ, once I tried playing peaceful games, I found that DA mode can be immensely punishing. Without DA mode, I can play through a one-city challenge and at least keep myself from slipping into a dark age, even if I don't chain together golden ages throughout the game. However, on DA mode, I have only once ever managed to successfully complete a one-city challenge. The only reason I was able to manage it is that Tamar was my neighbor and she kept trying to attack me. That allowed me to spam era score by getting unit promotions and also by converting her cities with apostles. The total era score from converting cities and from unit promotions was easily 75 or so. Without all that, I would have easily fallen into the dark ages and likely would have never been able to crawl back out.
I find the mode to really punish turtle strategy as well. Staving off the dark age the first time isn't too tough if one is paying attention. The second time, there are usually some easy era score bumps, such as lucrative districts and first unique units. After that, it can get out of hand in a hurry. Lately, I have been trying my hand at building a high population civ, going all-out on population growth. Previously, this was not necessarily difficult, it just took a while to really get going. Until one develops Urbanization, things tend to get a bit bottlenecked. Now though, I blow through the firs two ages. I even go out of my way to set aside some low level tech and culture advancements so I have them available for quick era score. But then, I found two or three cities and hit a new age and suddenly I need 90 ERA SCORE IN ONE AGE. I had 2 +6 campuses, a +5 campus and a +4 campus. I had Hildegard giving my two +5 holy sites and my +4 holy site science bonuses for their adjacency. I had science coming out my ears and the second-highest culture of all the AI civs (damn Scots). Even churning out science techs like they were nothing and making a fair run through culture, I still came up about 20 points short (anywhere from 16-26 depending on how I played). BOOM! There go two of my good cities. Oh, and now they have three military units better than most of my military and they are focused entirely on military production and causing as much damage to my civ as any barbarian ever thought about doing. They have heavy loyalty, especially since my neighbor also slipped into a dark age. So now I have an uber-powerful neighbor looking to harass me and they have enough loyalty that even my strongest combinations for applying pressure don't seem to bother them. Taking those cities back does tend to result in some era score coming my way, but not nearly enough. Furthermore, it requires essentially going into a truly aggressive posture in order to create a military capable of fending off the free cities that do not spend any time building infrastructure and revenue.
All-in-all, the DA mode seems to be hyper-oppressive to peaceful gameplay. Growing a large(ish) scientific civilization capable of competing on the world stage in diplomacy, science, and culture/tourism, is now exponentially more difficult and requires more than a little luck. Even without the loss of a WC government policy slot to use to help the science growth (if you want your golden age card), peaceful growth is about the worst of both worlds in DA mode. The growth increases the score one needs to avoid a DA (even if your civ is a full age more advanced than the nearest AI civ), while remaining peaceful eliminates an entire stream of era score (military advancement).
With the free cities working together as a single civilization, getting a massive loyalty boost, and a steady stream of high-end military units without the need to invest in any sort of growth or infrastructure, I am finding the DA mode almost broken for non-aggressive play. That, is a shame, as I sort of like the concept.
I do think there needs to be some sort of hard cap on how many era score points need to be achieved in order to avoid a dark age. Either that, or perhaps have a small window of score where a normal age still exists. The gold and dark policy cards are gone in that instance, but the cities don't go from solidly full loyalty to suddenly flipped with full loyalty and a strong military going the other way just because a civ is only mildly overpowering instead of fully overpowered.
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