Interesting tier list. I've been thinking a little lately about the difference between a T85 Xbow and a T85 CB with logistics and range. Which one is more effective? unless the Xbow is 2x the combat strength of the CB (ignoring the massive benefits of +1 range for a moment) then the CB is more effective right? even though its an era behind. Even against a good human player, veteran troops or UA's can alter this calculation. I actually also agree about the power of siege units to some degree. I find that a combined arms military (ranged, siege, mounted and melee) will quite often punch above it's weight when compared with how many of a single unit I would need to achieve the same result (with probably the exception of the mounted archers, they are too fast and too good to need anything else). Not to mention the benefit of having insanely promoted cannons ready to become artillery.
The importance of science has been over exaggerated for a long time in this game. It's undoubtably very powerful having a tech advantage, but given the potential multipliers in promotions etc. perhaps not the be all and end all. I'm not convinced that this game is as black and white as is often stated. I think often when a civ or unit is criticized, it shows a lack of understanding of how to leverage it's benefits. For example in this list the characterization of Babylon as a lower tier conqueror is perhaps underselling them. Their advantage lies in being able to either a) conquer with more advanced (higher base damage) units earlier or b) focus less on science during the early game and build more units to remain competitive. Their advantage comes in working out how to leverage their unique elements.
Similarly with the Mayan Atlatlist. You have stated that it's a useless unit. I agree you won't be doing much (if any) conquering with it. But you can build it from T1. You could potentially be earning promotions with them whilst other civs are still trying to tech archery. Surely you can see the potential here? They aren't great during their era, but they can make for great CBs and Xbows. Their lower damage means that if you are attacking a city state for example you can maximize the experience/damage dealt equation which is usually the limiting factor to how much exp a city state war will provide (once the city is at 0 health you get no exp for shooting). Their lower base damage can actually be an advantage if used right.
My overall comment is that perhaps this list needs to reduce the number of tiers in general. For any given scenario there are going to be complete standouts. In this example the Mongols, Huns and Arabia. They are clearly very good at conquest. Then there are those that are clearly bad for conquest. Personally, I think that is where I would draw the line. I liked the concept of what Consentient was trying to do with his ranking system, giving points to each unique as to how much better or worse it was than the neutrals. The implementation on these types of things is always difficult though. You have to look at the advantage each unique can potentially yield, and fully explore the differences in play styles required to leverage it to its greatest extent.
Canon promoted with logistic and +1 range are so funny, you just melt cities and once you're there, it's almost the end of the game... Yes I agree with science, people hardly understand it I don't know why, I won about 20 games on deity (domination) I lost just one (trying piety and rush archer but an AI snowballed insanely hard... and I ragequited) you can't really outtech the AI and have a decently big and strong army with many cities, people don't understand it. If you focus on science you'll be ahead, but then no early wars or not as good as it should, then you delay, then the AI spam cities, Units, and get harder to conquer, you delay over and over again and start war in renaissance, you'll have to make the game long, boring and use flight to handle it and you'll end arround atomic.
People can't stand babylone as being not good for domination IN the way that it doesn't help you at all. It's better to cross some really awful mounted as carthage than having a small tech lead. Plus, I'm often the tech leader in my games, because I conquer everyone before industrial, then I spam great merchant and I'm still fine, the only moments I need science is when ONE ai snowball and get flight before me and spam 20 great war bombers. Beside this, no need to be ahead in tech.
The early archer the mayans is ok, the thing is, you quickly get archer, in my japan LP I did it and take a city with archers, I think I had four. I needed stuff before that, worker, monument, granary, library, then archer. Getting them before could be useful maybe, but then I don't like heavily promoted range unit. I prefer sieges since they end the game quicker and it's funnier.
I did cover the god and top tiers, I just didn't talk about the GOOD tier because i'd like to write more, I'll do it later or tomorrow probably to explain each civ and my opinion about their places