First of all, thanks for all the detailed feedback. Feedback based on ingame playtesting like this is always highly appreciated.
I'll try my best to answer your queries.
What exactly does blockading a city do?
A blockaded city cannot heal, does not receive the bonuses from City Connections and takes 20% increased damage from all sources.
Some melee units, like the destroyer, have RCS promotions. Is this a bug?
Yes - but it's only a text issue. Two of them were fixed to say CS as intended in this latest beta.
Does the "Give me 10 rounds to prepare" properly work? In one game (normal gamespeed) the AI came back 15 rounds later and in another example (still same game) the AI never came back. Did it decide against going, even though we both agreed on going together, I don't understand.
You must be friends with the AI to start a coop war with them. If you end your DoF in the Discuss menu, denounce them or declare war on them (or they do any of these things to you), they will cancel their coop war plans. Also, they won't bother coming back if you're already at war. I'll look into the issue with the time counter.
About charts. Late medieval (normal, prince, huge) I was maxed out at 55 military units with 200 population (16 cities) and all military buildings while my eternally angry neighbor Mr.Zulu apparently had 25% more military might than me with just 100 pop (8 cities). I notice this every game now that other civs easily outperform in the charts and I know for a fact there is no way a small civ could have a similar army. But when using info addict the chat seem to be fixed, showing my empire has by far the largest military power. Is the ranking chart intentionally skewed?
Your military might is reduced when you have more cities; the logic is that you need to spread them out more to defend your empire, lest you go the way of the Roman Empire. Military score was tweaked recently for being too punishing. You can see the raw military power in Demographics (# of soldiers).
Have city states their own techs or from allies? Some are really weak and some very strong in terms of city defense.
I believe they do their own research, but I could be wrong about that. I know that the Barbarians gain a tech once 80% of civs have researched it rather than doing any research themselves; it's possible they use that kind of system. City-States
do get yield bonuses and cost reductions to compensate for only having one city to work with, though.
The AI was changed in the latest beta to prioritize Defense buildings more, so you should see more of them building Walls etc.
Also, a City-State that a major civ has Pledged to Protect gains a 5% CS bonus per PTP, up to 25%. Siam's unique ability gives an additional +25% CS to City-States they're allied to.
I don't have a comment on every individual point for your feedback, but I can say a few things:
Air units should not be affected by roads and railroads.
If roads/railroads have any effect on air units, that sounds like a bug that should be reported on Github.
Upgrading from Explorer to Zeppelin is way too expensive.
I agree with this based on my own experience. The Explorer -> Zeppelin upgrade cost is huge.
Asking an AI for public friendship and getting declined should not disable me from asking again. This leads to me never asking any AI out because even if they are very friendly, they may decline and either of us can't ask again for many many rounds so I don't even bother to ask them anymore, I just let them ask.
This has irked me for a long time as well; I'll see what I can do to fix it.
City states need more units. They can easily be conquered by 1 AI city.
They start with 0-3 melee units based on difficulty level, and they get certain Production bonuses, but they have a unit cap and they're not meant to be formidable opponents. That's why they rely on major civs to protect them from big bad Genghis Khan.
Great Wall should be ineffective against players that have Dynamite.
This is a vanilla thing that doesn't make sense to me, either. The adversaries are the ones breaching the wall, so whether they've researched Dynamite should be what's considered.
Vassalage makes little sense after a change a few months back. Now the AI still doesn't want to peace out for surrender even after losing their capital + a few cities. E.g. Suleiman had 7 cities. I took his capital and his 2 best cities and only after taking another one he surrendered. This needs fixing. This feeds into that the problem the AI also forgets it lost a few cities in the previous war so making a short peace treaty resets that requirement. I think losing the capital and maybe 1 city would make everything okay again and still better than just the capital which can be cheesed.
I think they require a total war score of 90 to consider capitulation and 100 makes it guaranteed, but I may be wrong about that.
The pioneer and colonist are way too expensive compared to a settler. What is it, like 5 or 6 times the cost of settler?
The cost was reduced in this latest beta.
Renaming the "Refuse" button to "Decline" would fit much more in most cases.
Well, they're functionally identical, but I agree with you, haha.
