So, I've been thinking about the different magical societies of the mortal (playable) races of Azeroth and trying to see how they fit together, wanting to understand why what you expect doesn't always happen, like the kitin'tor leading in some areas where you would expect one of the elven orders, or why the highborne seemed so pathetic for the night elves when they were introduced.
Sometimes we can be quick to blame sloppy writing because it doesn't fit our desires (or head canon more harshly) and that sometimes is perhaps an indication of laziness - that deeper investigation might reveal a logic tot his than immediately meets the eye. I've noticed blizzard tend to be like that, it may not come across straight awya because it is not outright stated but there is a lot of logic to everything that happens and the deeper you delve into it , the more sense it makes and you realize perhaps you were the one being sloppy, not they, and the clues are all there, you just have to find them.
Magical Orders:
Kirin-Tor (active)
Order of the Tirisfal/Guardian (defunct)
The High Elves/Blood Elves (in-recovery)
The Highborne/Nightborne (in-flux)
These are the 4 main magical bodies that I can think of in the wow universe, the rest are either too small or just not powerful enough. The draenei may have some incredibly knoweldgable mages, but their people group are not really focused on magecraft seeming to excell more at Priesthood, Paladins, Shamanism and Jewelcraft/Crystal specialsts and technologists.
I think I understand why the Kirin'Tor is the most powerful or rather most effective magical body atm - it's because it has benfitted from the best of Dragon and human mage craft as well as High Elven. 2 of the most prolific dragon spell casters - Krasus and Kalecgos have inputed into thhe Kirin'tor allowing a huge amount of kowedge to accumulate.
The order of the TIrisfallen got folded into the Guardian and Karazhan - altho only 1 person was properly instructed there, the guardians seem to inherit not just the power passed down by the mages but the knoweldge also, as some of those mages were high elven and ggiven the threat of demons, these would not have been low grade ones, one can imagine what they accumulated in the centuries sicnce their forming. Didn't Aegwyn find refuge in Karazhan - it seems to ahve a library that rivals the Kirin'tor, and hosted the most powerful mage in the known world.
The high elves/blood elves - use to be an incredible body of their own, whiles they would send and often have students of magic like Priince KKael'thas go to study at a place like the Kirin'tor highlighting, the masters of magic and brightest schoalrs of their race, the ones centuries old would be at the royal court or the High elven council of mages at Queldanas in teh SUnwell, lead by King Anasterian Sunstrider - thankst o the betryal of Darkhan though, they suffered significant losses to this order, and though the blood elves have risen up from this, where I would have siad pre 3rd war the high elven order surpassed the Kirin'tor, or at least measured to it - post 3rd war, it finds itself weaker. Remember the High elves were not just a city nation of wizards, these were millennia old magical society - their output befor etheir fall would have been more.
The highborne/nightborne - in some ways, the highborne of hte shend'relar would have been the most knoweldgeable, still of the era of magecraft that produced wonders and a civilization unparalleled, they were (until Suramar) the only group to have continued from that age, even the high elves had a 3,000 year gap when they were part of the Vigil society and magical usage was banned, before gettign exiled and having nothing of the past but what was in their heads, had to build anew. Not so the Shend'relar - bthat city was where the Queen's most powerful projects were processed in secret - what Illidan and Kael'thas botch up in fel energy usage, they mastered 10k years ago in trapping Imol'thar and funnelling it's power - and we see they didn't develop fel mutations by it, which speaks to the pedigree of their skill. But, the demon corrupted them, by the time we meet them, Eldre'thalas has fallen to ruin, and they're just really hooked on magic, most of the city , it's power , it's knowlege in ruins, they maintain a small libarayr. A few uncorrupted highborne escape - but we find out that their knoweldge is rather outdated compared to what the blood elves know. I've thought a lot about this and concluded this must be because they went stale when their city started falling to ruins, furthermore being scholars and a small city, in isolation they would not have been developed in some key areas, particualrly magical combat- not having to fight wars etc... As for their reserach, it would have stalled with their problems and their addiction.
However, since the introduction of the nightborne - we see what teh Shend'relar and the night elves could have been - and here we see a soceity that did not fall to lusts or recklessness and addictions - they continued advancing from where they were 10k years, making them the most advanced magical society on Azeroth - having a huge city, and the resources of a well too, - being in isoalation would be limited, but they are the true zenith point of the highborne and night elven peoples.
But how do they compare with the others? Well we know blue dragons use to enquire and ponder the msyteries of magic with the night elves in Narth'alas and Suramar before the fall. so they have a lot of knoweldge, the blue dragons also go into isolation for 10k years, which is why the night elves of the vigil did not discover they were erroneous concering magic, while Karasus has been with the Kirn'tor for a long time, Kalegcgos is only been involved recently - so the advantage of the dargons to the kirin'tor might not be able to offset the capability of the nightborne. We note taht amongst the highborne - whehter Shendrelar, nightborne, moonguard, or Court of Farondis - mmagic is good, the moonguard though overwhelmed by the legion aligned portion of teh nightborne seem to be more competent and skilled with magic than they - but then the moonguard are combat specialists that had bene going on for 10k years albeit without hte resurces the nightborne had. The order is lost, but the survivors are helped by the nightborne resistance and team up with Thalyssra who takes them and other night elves under her wing in their efforts to defeat Elisande.
Many Eldre'thalas and night elven knowledge thought lost were been sold off by the shen'drelar zealots, that knowledge is likely gathered by the Kirin'tor - however much of the nightborne knowledge will remain unique to that group, the highborne/nightborne would not be privvy to the advancements of either the blood elves nor the Kirin'tor as they would not be privvy generally to much of their knowledge they would have, don't forget the night elven group have had 10k years to advance their knowledge and though the shend'relar fell to decadence and ruin, neither the Moonguard, nor the Nightborne, did.
So there you go - the magical orders of Kalimdor. At the moment as of Legion it looks like it will be 3 main ones
Kirin-tor (Order of Tirisfal & Guardian folded in) - neutral body avilable to all raes
Blood elves (majority of the former High Elf group in here too) - They continue to build up and flow up
Nightborne (Moonguard, Highborne, mage night elves folded into this) - provided Elisande and Gul'dan defeated by Thalyssra's nightborne resistance and the allied force of heroes) this should be the 3rd major magical order - and would be the oldest of the 3 too).
The Kirin'tor now has it's knowledge combined with that of the Order of Tirisfal - but both the Blood elven and Nightborne/Highborne orders are far older and well, still have intact knowledge.