I like your analysis it seems very well throught and structured however everything could be understood if you look at it in a different way.
Anachronos: "Is it time for you to visit me already? Yes, I suppose it is then."
Take this for example, the hint is in his question. Now I had this asgument before about how WoD should have never happened since a bronze dragon was the cause and they were supposed to preserve the timeline and not mess with it. However the moment that event happened and connected to our timeline it became part of it.
Which means Anachronos from his vision of time he knows that the mag'har were supposed to come to our reality. So when the horde player goes to him and asks for help to him he is mearely keeping the timeline in the right flow because that is how it is supposed to happen.
Anachronos: "It was there that Gul'dan used a piece of the Vision of Time to travel between realities."
This is also when you think about it not that far fetched. Although it is true it was not explained how the Gul'dan came into possession of the shard, we know that at the beginning of the HfC events Gul'dan had emprisoned Grommash so it is not that far fetched that he got it off him then. And at the end it was used by archimonde to send him back to our Azerothe.
Eitrigg: "Durotan was chieftain of the Frostwolves. Never have I known a more honorable orc. He was a true leader who loved his people. I miss his wisdom."
Although Eitrigg might have not gotten too much contact with Durotan, however the latter was a very well know character in the old horde for his constant defience to first the formation of the horde and not fully embracing the war against the Draenei.
Also as you mentioned one other Blackrock orc had a much closer connection to both, Orgrimm, who really valued Durotan and held him to high esteam.
So one doesn't really need constant contact with another to miss his wisdom.
Eitrigg: "Heroes from my world once freed yours from the grip of tyrants." Now Azeroth faces a similar threat"
As for this, since Eitrigg is talking to Grom himself he obviously not referencing the iron horde but the Gul'dan and the legion. He obviously referencing Grom's "Draenor is free" from the end of HFC.
Eitrigg: "Now Azeroth faces a similar threat"
He is obviously exagerating the reality to get the help he needs. So why is this inconsistant? Someone asking for reinforcements in a war of course he will paint his side as the innocent side and the enemy as the monsters. There's nothing inconsistent about this.
Eitrigg: "You are the daughter of Durotan and Draka. I see them both in you."
As mentioned above Durotan and Draka were very well known amongst the old horde.
Geya'rah: "My father fell in battle to the Lightbound."
Shifting Alliances:
Once Gul'dan was killed the Draenei and the orcs remained on good terms. And Grommash decided to keep the horde unified in order to fight the remenant of the legion. Which from the scenario seems to have taken a not so short amount of time. In that period it is not that far fetched that Grom earned himself redemption for his past actions.
Geya'rah: "But without demons to fight, the draenei became fixated upon their precious Light. Their naaru masters compelled them to spread their influence among the orcs."
Inconsistent characters:
You can't say something is inconsistant and start your argument with assuming. If you open the door for assumtions you give up on inconsistancies. Also even if the characters are same their personalities aren't necessarily the same if the circumstances change the ones we met in Outland were in a very specific set of circumstances so you can't really expect them to behave the same.
Geya'rah: "The tyranny of the Light must be ended!"
Inconsistent portrayal:
In our reality and our interactions with the light we only faced the gentle face of the light. Or the naaru to be exact since the light is merely a primordial force of nature that can be used for good or bad, after all the light is used by priest and paladins as a weapon.
Also from the "thousand years war" audio book we get to visit worlds that were inslaved by the light and turned into cristalized barren deserts.
Geya'rah: "No... a naaru... Not again!" (as a Naaru casts some sort of area attack, shackling every orc. It is implied this will result in them turning to the Light.)
Inconsistent abilities:
This could simply be the same spell that X'era tried to use on Ilidan. Which makes it not that inconsistant.
Exarch Orelis: "Cease this pointless defiance, Mag'har!" (Entering in a Warframe)
Impossible technology:
Again assumption. You are assuming based on knowledge you have in a very specific set of circumstances. Once you remove those ciscumstances everything becomes possible. Also the draenei are a technologically very well advanced race if the few on Azerothe managed to create the Vindicar the ones remaining on AU Draenor have a better chance to create way better than warframes.
Geya'rah: "[...] until Draenor is free!"
It is not necessary that evry line is a reference to something else. Once you meat the Mag'har they are all that is left in a long war. So It is safe to assume that the other races were converted as well so it justy could mean what it is "until Draenor is free"
Yrel: "The Light Mother has blessed me with visions."
Impossible contact:
This is explained in the Chronicles 3 in the definition of alternate realitites. Basically That AU revoleves around draenor and what is happening on it, there is no Azeroth, so there is no alliance expedition no Turalion an Alleria no war on argus the only mission of the light becomes to spread on Draenor.
On the Draenei's supremacy over the planet
Inconsistent numbers:
Their suprimacy is based on the m being the once that are calling the shots. And as explained they are very advanced race with help from the very powerful being. Also they didn't start the war right away the y started the conversion by preaching and taking in those who embraced the light willingly many among them are orcs and other races them used them to fuel the war.
Grommash: "It is the Light that has doomed this world!"
Inconsistent portrayal:
The Light and its worship is ancient. The Draenei have been following it for millenia, and the humans centuries. It has saved the world on several occasions, and protected life more often than not.
Yet, after 30 years of Light worship on Draenor by Yrel, the planet becomes Light corrupted.
Actually the draenei only started worshiping the light after their exile from Argus. Priod to that all their civilization was based on the arcane.
Again the light is merely a primordial force of the universe it has no will the consequences of it's use falls on its weilder. Until now we only seen it in contrast to other powers used to nefarious goal. However in AU Draenor it is the only strong force unopposed unchecked and the naaru used it in the wrong way.
Yrel: "It pains me to lose an old friend, Grommash."
Thematically inconsistent:
35 years is the difference between the two events. If Grom attoned for his crime by helping Yrel fight the legion for 20 years then lived in peace for 10 years then the war started that makes him an old friend of hers. Nothing inconsistant about this.
Sylvanas: "I trust honor means as much to you, as it does to him?"
In before the Storm it is stated that despide the fact that Sylvanas does not feel honor, or undertand it fully because of her state of undeath. She still remembers what it used to be and values is in others.
About the "Mag'har"
Thematically inconsistent:
This could be a reference to them refusing to drink the blood on two occasions. Once at the begining and the other at the events of HFC.
Anyways you are simply reading way too much into it. It is simply a 30 minutes tops questline the informations given serve the intended purpose to get the Mag'har. Nothing in it really is way out of the way some information is simply not fully given to keep the length of the quest chaine consistent with the others I guess.
The biggest point that could be considered a mistery is the Gul'dan with the vision of time everything else could be considered nitpicking tbh.