Firstly, you need to compare them to archers, because those are the closest in castle age. When you do that, you will realize why they are so special. They are similar to archers in that a few of them don’t work that great. This is also true for other S-tier units, like the ballista elephant and urumis. A few ballista elephants will get shredded by halbs, heavy cavlary and siege. But get a mass of 20-30, and you have a death ball, which can only be stopped by siege onagers or certain UUs. Urumis will get destroyed by pretty much anything in small numbers. But get a mass of them, or combine them with other infantry, and you have a very strong army. So we’ve established that this “work in small groups” is not a criterion for getting S tier.
This is another statement you’ve made, and this is precisely where janissaries are exceptional. If you have 10 archers, you have a force which can take villagers down from a range, but will die to cav and can’t really take down buildings/cross walls. However, it is trivial for a force of janissaries to destroy walls and take down buildings. They are obsidian arrow archers on ######### If given time, they will destroy a tc without losing a single HP. They can deal with cav unless they get run over, but turks have light cavs to act as meat shields. This means the knights can’t not take the fight, when you are in the eco and destroying tcs.
You forgot that their damage is 22 in the elite version. I agree with you that Bohemian hand cannons are great in castle age. But, Battle Elephants or cav archers would be OP in feudal age. They get the same unit an age prior, and that unit is extremely powerful in the prior age doesn’t necessarily mean that the unit itself is S-tier. To take an extreme example to make my point clear, take any of the C-tier UUs and place them in dark age. They would be oppressively strong. Does that make them S-tier?
Also, while you don’t need a castle, you do need to build a university and buy chemistry, which is 100 wood for uni, 300 food and 200 gold is which is almost the same as the cost of a castle, especially considering how tight food is in the early castle age. HCs don’t outrange a TC either, which is a huge downside for them. You need something else to deal with TCs.
You don’t need mangonels with Janissaries, get light cav instead. Janissaries can take down a TC by themselves. Light cav will take care of all those running vils. Now, that all being said, placing them in A tier is fine. I consider them somewhere between A and S.
I disagree completely. Your logic doesn’t work because civs don’t work that way. Let me illustrate with an extreme example. I’ll make a new civ, with burmese as the basis. I’ll make a new UU, and let’s say it has 500 HP, 45 melee attack, 0.9 movement speed and 15/-2 armour, costing 100 food and 80 gold. Now, I’ll add a “bonus” to the civ as follows: “villagers move 15% faster, but take +100% time to create”. Is this new UU S tier? In the hands of a civ like britons, absolutely. But in the hands of the new civ, it’s nearly useless. This new civ will be bottom tier in all 1v1 arabia games, because your civ will never get to mass these.
This is an extreme example, but an in-game example is Dravidians. Urumis are an exceptionally strong unit. It is the most cost-effective melee unit in the game (except maybe vs Persian elephants). But Dravidians are a bottom tier civ. A UU does not make a civ S tier, although it can certainly help.