Khevsur & berserker suffer terribly from the their combat effectiveness vs production cost ratio; as well as being like most units: complete crap compared to knights.
But we are a data driven bunch, so let's crunch numbers.
First, we will need to know how to compare two units in terms of their raw
Combat Effectiveness. A unit that deals twice as much damage would be twice as effective. A unit that deals twice as much damage
and takes half damage, is 4 times as effective. (Basically how much damage a unit could inflict against an endless horde of 1v1 baseline unit combats before it dies.)
Well, this is exactly what the Civ6 combat formula does; it just computes a damage factor (taken & received) based on the strength difference of the units fighting. So if a unit has a combat factor of 2, it will be four times as effective (see above reasoning.) Incidentally, any Army is 4x as effective as its base unit, because +17 strength is a combat factor of 2- so combat effectiveness is 2^2=4. Okay you pedants, it's like 1.97. But for all we know, they manually tweaked the table. Anyways, my side point is that corps and armies are actually efficient uses of your production. Especially when you get military academy discounts!
FYI, the combat formula is
Damage = 30*combat factor* Rand(0.75,1.25)
where combat factor=e^(Strength Difference /25).
Essentially, identical units will deal 30 damage to each other, plus or minus up to 25% noise they toss in to spice things up. Combat factor is a multiplier that determines how much damage you take or receive.
So, if we know the strength of two units on the same upgrade line, and we know their production costs, we can compute how efficient that upgrade is. A unit that is twice as effective and costs twice as much would be an efficiency of 1; greater than 1 implies you're getting more bang for your buck, while less than one implies you're actually better off not upgrading and making the outdated unit. This would also work for units between lines, but let's focus on upgrade lines for now.
Here's three of the direct combat lines, indexed so the first unit is 1. Combat Effectiveness is the increase over the previous unit; note that I have muskets compared to swords and not khevsurs here. Efficiency is the Combat effectiveness vs the production cost ratio; Combat efficiency * (Cost_New/Cost_Old).
We see that almost universally, 1.5-2 is the efficiency of upgrades for almost every unit. Except knight-tank (more on that), spear-pike, and sword-khevsur. That 1.5-2x figure probably relates as a good heuristic to track how players production capacity isn't growing quite as fast as combat power is, so to keep units taking about the same number of turns to make over time they increase the efficiency.
Knight-tank is skewed because the difference is so large. It's essentially two jumps at once, so it's like a double 2.2x upgrade. It's the same kind of jump as anti-cav was before pike and shot existed. They should really insert an industrial heavy cavalry unit...
Pikemen universally are known to cost way too much. I'm surprised they didn't fix it in R&F. For their strength, they should cost ~130-150 to be on par with other upgrades. This is also why the Impi are actually good units (they're 1.87x efficient.) Pike & Shot look really good because it's only a 25% cost bump for basically triple the meat.
But notice Khevsur: they are the
only upgrade with an efficiency of less than one! The leader who builds khevsur instead of sticking to swords is actually only 70% as combat effective. What?! Even fighting only on hills, they get a 1.2 efficiency- basically on par with spear to pikes.
Conclusion: military tactics units cost WAAAY too much for their strength.
On the aspect of walls, I agree that Tsikhe are too pricey too justify cool looks and +3 faith. Unique walls are a cool concept, but they should probably be normal price with Georgia getting +100% towards walls in their ability, or something like that.
