Ok so help me out here. The Aspects and Primals are all from the same clutch and all got their power from the Titans.
Life
Magic
Time
Dream
Neltharion the Earth-Warder - is he more primal then aspect? Is he the link between the two factions?
Fire
Lighting
Wind
Water
That is actually a good question, he could be, maybe?
I personally have not find any lore that supports it, but he does look the part as Deathwing!
I honestly have a lot of question after my playthrough as Dracthyr. 
Same here. Itās why I plan on leveling and gearing my dracthyr first. I am hoping there are special interactions or dialogue for dracthyr characters
Neltharion having earth powers is an interesting observation but thereās actually already an earth Primalist. If you look up Iridikronās model on wowhead, heās made of stone:
https://www.wowhead.com/npc=185407/iridikron
And this is a side tangent but theyāre not all from the same clutch, Ysera and Alex are the only ones biologically related. Alex said she and the Primalists were āas close as clutchmatesā, meaning not actually related but such good friends they basically were.
I definitely think weāre going to learn more about the origins of dragons and see more of Neltharionās legacy but I donāt think this is it, honestly.
I know of at least one questline that has unique dialogue for dracthyr (minor spoilers, itās a sidequest not main story) (Spoilers) DF sidequest: The Black Locus
The primalists and aspects are not actually from the same clutch, they were just as close as siblings. And there is an earth primalist too.
Deathwing also got his powers from the titans like the other aspects, while the primalists dwelled deeper into their own and Azerothās elemental energies.
The primalist viewpoint is that they donāt wish to subject themselves to or serve any outside force. Dragons are meant to be free and not enslaved to any cosmic force.
They disagreed when the aspects agreed to serve the titans and infused themselves with their order magic. They disagreed when the keepers infused Azerothās natural lifeblood of elemental energies of change with order magic. And they disagreed with exposing eggs to the now order-infused lifeblood making any future dragon align with the titans philosophies.
It was at this point the primalists were really formed and they demanded that Tyr was to be banished from the clutchlands (dragon islands) for his tampering with the waters etc, but the aspects refused which led to the primalist rebellion, and the primalists got locked away instead of killed since the aspects didnāt have the heart to kill them.
And now with the awakening of the dragon isles and the primalists getting active again, they want to purge Azeroth of the titanās ātaintā, which they view was forcefully imposed upon it.
Neltharionās charge was protection of the world, which gave him as a part of that package control of the earth, but it is an arcane ability to warp the earth. Iridikronās power is a pure elemental tie to the earth.
Its akin to how a mage can throw fireballs but it isnt through using the same mechanism that a shaman uses to do the same thing.
If your a shaman doesnāt re-empowering the aspects go against your religion just a bit?
Re empowering the Aspects is honestly against most races and groups best interests.
-Neltharion almost tore azeroth apart and was corrupted by old gods, also all the flight
-Ysera also was corrupted and needed killing also a number of her flight have also been corrupted.
-Malygos went crazy and almost destroyed the world by making all the arcane go to one point. Most of his flight went crazy as well.
-Nozdomu is also going crazy along with half his flight and screwing with time it self.
-Alexstraza ended up captured by the Horde and her flight used by them and by extension the legion to try destroy the world.
Now we are getting a new bunch of lore about more evil dragons that have gone evil from being empowered. Best we make sure no dragons end up with any power as they ultimately all go evil from it. The Power should be passed to mortals as at least they are easier to deal with than super powered dragons. This would be a better follow on from cataclysm which had the dragons give up their powers. Having the previous Aspects coach the new Mortals as well would be interesting.
I donāt see why it would. Before his downfall, Neltharion was on good terms with Therazane and the other Earth Elementals according to Kor the Unmovable.
Side note: I like to imagine that Neltharion tried to study under Therazane in an attempt to control and contain his powers. I just like the idea of Neltharion making his bargain with Nāzoth as a last ditch effort. He tried other methods to either remove or numb the pain he was experiencing being the Aspect of Earth. But none of them worked. Meanwhile Nāzoth was whispering, āTold you soā the whole time. With no other choice he made the deal with Nāzoth. Usher in the Hour of Twilight and the curse will be removed. Of course we know exactly how Nāzoth was going to make due on his promiseā¦
We just came from an expansion where a mortal empowered by a cosmic force tried to destroy the entire multiverse, preceded by another mortal from another timeline working for another cosmic force also tried the same thing soā¦ mortals are not doing so hot either on that front. Perhaps the solution lies in a check and balance between mortals and dragons.
No. For one, Shamans donāt simply worship the elementals. They worship the spirits of the elements. Elementals are included in this, but there are also ambient spirits inhabiting the elements as they appear normally. Shamans can communicate with the earth beneath them or the fire on a torch. Unless the Titans or Dragons actually harmed the elements, the shamans wouldnāt be opposed to it at all. Keep in mind that this entire explanation leaves out the more death oriented ancestor worship aspect of shamanism.
Funnily enough, the Titans āimprisoningā the elementals in the plains actually ended up benefiting the elementals overall. They were freed from the Old Godās control and came to like their new homes more anyways.
I kinda always headcanoned that he was the Speaker before Magni
Thatās not a headcanon, thatās actually what Deathwing says in Charge of the Aspects. That he could hear Azeroth and feel her pain as his own, not unlike how Magni can now as the Speaker.
Yet mortals werenāt granted the powers of the Aspects for the specific purpose of protecting the planet. Plus the Ratio of mortals who have gone bad vs the Dragons is quite minimal in comparison.
Lightning is teamed up with the wind, not in a separate elemental tier ā Much like Ice teams up with water or Magma teams up with fire. 
ā However yeah, Neltharion being the Earth Warder still begs the question whether heās more primal-focussed power than aspect.
Aspects are Aspects because of who empowered them. Had Golganneth created an Aspect with storm powers, that would not somehow mean said Aspect was a Primal.