I am not saying what you see is reasonable or intuitive, but these are not bugs. A bug is an unintended consequence or anomaly caused by a developer.
Of this I am 90% sure: I believe it is the same calculation system that has always been there that drives the battle outcomes. Take a look at the statistics distribution of Ahura units compared to Persian units. Besides the general scale of the offense/defense, you will see that it is very differently distributed. Also, the relative strength of Elysian units between each other, have changed. These things influence the battle outcome. To understand the results of what you see, you need to understand the battle mechanics - how they have always, actually, worked. I am not saying that what you are seeing is reasonable or intuitive (because its not). I'm rather saying it is not a bug, based on how I defined a bug above. It is also important whether you compare results from an off/def position with each other. I might as well argue that it is not reasonable or intuitive that it takes around 100 Javelins (grown men, with beards, armed with spears) to kill one guy on a horse either. Also, how do you feel about the hugely powerful scouting guardian, with only one eye?
Of this I am 100% sure: While I am writing this, I might as well clear up something on rewards on Elysian Positions. Complaints have been made that the rewards are broken. Again it is the same core calculation system behind the rewards. What has changed instead (compared to the Persians) is the resource to offense/defense ratios amongst the Elysian units compared to regular units. In other words, the inputs to the system have changed, not so much the system/mechanics themselves. For Elysian units, these have been set in such a way where many position strategies will struggle much more (compared to Persians) to break even on offense/defense. You will break even on resource value, like you always have with the Persians. From the very beginning, the intention of the Persians has never been to be a source of growing your army. It turned out to be a great source of growing army power (even without reviving units) if the Persian system was exploited a little. Potentially, Plarium implemented the Elysian positions to be as they always intended positions to be. Again, I am not saying this makes sense from a game design perspective (because it really doesn't - the concept of playing to lose is very strange, unless you could hit a jackpot like in a casino). Just explaining why you are seeing what you are seeing.