We can't consider something in isolation. Who in their right mind would make a bunch of Keshiks without making Gers first?
Also, we need to understand that the game designers knew about the Ger when they decided what bonus to give to the Keshik. They knew Keshik/Ger would be going together and the bonuses would be additive.
And what do your settings have to do with it? That's a really confusing statement.
Yep. But I'm not considering any UU in isolation. All comments were considered together with the leader and even the free techs.
About this keshik matter, I said like this shortly: Mongols are strong but keshik not that much, which means mongols are still strong and keshik is a nerf. if keshiks had a free promotion, mongols would be overpowered togetehr with other factors.
About settings issue, maybe you missed the comments between me and micmbk. i simply believe that in marathon fastness is nerfed a little bit.
keshik should be stronger in speeds faster than marathon, such as fast worker.
building a road on forest with worker in marathon: 9 turns+1turn move into the forest
building a road on forest with fast worker in marathon: 9 turns (the 1st turn fast worker moves on the forest and start building road)
the efficiency here makes 10/9 whereas in faster speeds it is 4/3 and sth similarly.
But of course if you have high number of fast workers than the efficiency practically increases, considering you move as a stack.
depending on civics/unit costs, in some games i have workers twice # of cities, and in some eras (mid game for ex) even more than that.
Since TheMeInTeam taught me the correct way to do a rush with War Chariots, I have used it often successfully. The warmongering part is now easy for me even at Emperor, but I am still working on how to manage the economy during and after the first war. In my current game Monty built a city right next to Thebes that is covered with jungle. It would be a drain on my economy until I get IW, so I decided to raze it and come back later -- after I get IW -- with a Settler on that spot. I wish somebody would start a thread on the economics of early warfare. That is my biggest weakness now.
Yes. economy

That's a very important issue about high levels. But I believe more than economics of early warfare, midgame economy is hard at high levels.
High difficulties favor wars more than easy levels. economic/scientific AI boosts change enormously per each difficulty level up while combat odds are not that much effected by difficulty. So AIs have to be continously disturbed. If you let them grow peacefully, most of the time they easily beat you in tech.
as the main parameter behind tech is the sum of beakers, being large is the key. but how to do this (when to expand) in higher levels seems like a learn-how experience. You should play much. Keeping a balance between economy and expanding is hard at high levels but i believe you shouldn't give up expanding anyway.
you have to be large, but what is the tuning of it, how many cities? Well, I generally let AIs beat me in tech during mid game, and expand. In early game, they already start faster. I mean, I kill a few, yes, but some AIs which aren't on my continent beat me in tech. You can understand this from religions found and wonders built. So what I generally do is letting some AIs beat me in tech during mid game and not loosing control on motivation and strategy, not to get pessimistic

i just continue warring and try to expand.
the more you expand in mid game, the more back you get in tech. I try to set the expanding tuning such as that i'm not very very behind in tech. if you haven't been enourmously behind, you can catch them after mid game. economics of a large country is such in my games on high difficulties. in monarch and below, i am generally ahead of everyone in tech allover the game.
i'm playing my first deity game with Huayna Capac nowadays. I killed Khmers very early and the French in ~2000BC. I finished scouting the continent and there is no other AI. I assume, 1/2 of the AIs in other continents might also have been killed by barbs already. I have the great wall and the pyramids. I paused at ~~1500BC when mids is complete. Just before I got to bed ~1500BC, i heard that Christianity is found.
i'm very uncomfortable with that. I have no AI to attack. The pottery is about to come (i researched some other techs before pottery as it wasn't essential yet at that moment and even with a FIN leader i don't start cottaging in early game). I hope i will get fast in tech after that.
I'm sure the game would be much easier if i played on a pangaea map on standart world size. i would kill 2 AIs and then i would disturb the remaining 4 (4 or such. was it 7 seven players in std?) AIs continously. I would make small attacks all the time and they would come back gifting me GGs. Then after each military tech, I would kill another AI. This plans seems much simpler. Economy is hard in deity.
For the ones who would be interested, here is an attachment. an excel sheet with formulas and also pdf formats. "xp guide v2"
http://forums.civfanatics.com/showpost.php?p=8843591&postcount=114