AfterShafter
Deity
Praets are no more of an investment than a regular swordsman (except for the higher base cost). Do people not build swordsmen at higher difficulties? Also, the only 2 move units before tanks are the horse units, workers, and settlers, and the horse resource is even rarer than iron.
Of course people use them on high difficulties - in conjunction with other units. Mainly catapults which, when you have them, make the base strength of the swordsman type unit way less important since the siege units do your heavy lifting for getting cities ready to be taken. This arrangement is why Praets don't shine, and don't do anything special on deity - because, take away their pre-cat rushing ability and all they are is a stronger unit where a stronger unit isn't needed.
As for Levgre, same deal... Why are Praets *so* wonderful if all they really do is slightly bolster an already effective strategy in medieval war? Swordsmen, which are cheaper and have an equivalent 6.6 str attacking a city get the job done when paired with cats.
Iron more common than horses... Maybe - but it's much cheaper to see if you have horses than iron. As in, if I decide, on Immortal or Deity that I'm going to Praet Rush or something, I have to commit myself to relatively a lot of teching that may not help me out in that absolutely game-critical early game... Unless you're inundated with jungle OR want swordsmen fast, you don't need iron working right off the bat generally. On the other hand, the wheel and animal husbandry are two basic low level techs that help you establish your early empire. Going for them early is very rarely a waste - it's something you were going to do anyways.
I stand by my position... Praets are a cumbersome unit, and Deity - heck, even Immortal - pretty much strips them of their sure-thing pre-cat rush ability. That being the case, their `power game`becomes being a slightly more powerful backbone to an army makeup that works well without them. They`re nice, but they're not by any means game breaking.