To disclaim, I am by no means an expert player, and I’m as much posting this to find out why I am wrong as to prove to you that I’m right
Obviously knights, particularly Royal Knights, are quite controversial at the moment. It seems almost inevitable that this is going to lead to various nerfs once Relic starts patching the game, but I’m struggling a bit to see -how- these units can ever be balanced without a significant rethink. It’s one thing to balance them in the early game, but they are enormously far away from being balanced in the late game too.
Right now the immediate problem is that knights are too strong from a cost efficiency point of view. It is very hard to deal with knights for less than the cost of a knight, even if you know exactly what is coming your way. Their hard counters, spearmen and crossbowmen, can be built 3:1 and 2:1 respectively for the same cost, but actually fighting knights with those numbers leads to at best pyhrric victories. This seems at odds with the concept of a hard counter. If you end up in a battle where your opponent’s army is a hard counter to yours (e.g. you use a lot of knights and they use a mass of spears and crossbowmen) you shouldn’t simply lose you should be left in tatters. And that isn’t happening right now and that clearly needs to be addressed.
But even if the cost efficiency of knights was more reasonable, it wouldn’t get away from the equally serious problem that knights are much more pop efficient than the other core units. The other five core units (the archer, crossbowman, spearman, man-at-arms and horseman) cost 80, 120, 80, 120, and 120 resources respectively. The knight comes in at a massive 240, and that leads to a scenario where once you start pushing near population limits the knight becomes a no brainer unit even if it gets appropriately nerfed.
If you need >100 units to counter 50 knights efficiently (i.e. by using the units that are designed for the job) the reality is you can’t actually counter fifty knights efficiently. Sure, you can build an army made up of fifty spearmen and fifty crossbowmen and you might just about beat fifty knights… but if they have anything else you’re going to get massacred. And you will get massacred because an army designed to defeat knights is incredibly vulnerable to other things. The only general purpose solution to “my opponent has a lot of knights” is “have a lot of knights” because it’s the only way to mitigate the massive difference in strength that you can have with knights, and without, given the population limit.
The basic point is that even if everything is well balanced from a cost efficiency point of view, there are still going to major issues in the late game if there isn’t also balance in terms of population efficiency. When the cost / population of units starts to vary wildly, things break down pretty fast. The five other core units in the game represent 80-120 resources per population. It stands to reason that the knight needs to be around the same place. That can be achieved by making a weaker, cheaper knight, or it can be achieved by making the knight take two population rather than one.
Obviously AoE4 already features several units that do take more than one population. Siege units take three population each, as do elephants. These units range from 133 cost/pop all the way up to 333 cost/pop. The argument I’ve created above to show why I think knights’ population efficiency makes them imbalanced would also suggest that the more expensive siege units and elephants are also imbalanced, which I’m not sure I believe. But I do think there is one fairly clear differentiation here in the sense that these units are very different from the knight. They are high risk/reward units where the knight is the most versatile unit in the game.
So that’s kind of where I am at with respect to knights. I think it’s a shame that they are so dominant that it feels like you have little choice but to start amassing your own as you reach late game. I’m a little surprised that they are such a massive outlier compared to the other core units in the game – but I do think having them contributing 2 pop would be a pretty good way of balancing their mid-late game strength.