Here’s some more direct quotes about the Highborne then from Well of Enernity since you’re pretending to put so much stock in direct evidence:
He wore body armor of molten steel and in his huge, gauntleted hand he wielded a whip that flashed lightning whenever used. His chest and shoulders, so much wider than the rest of his torso, dwarfed those of even the mightiest warrior. Wherever the armor did not hide his form, pure flame radiated from his scaled, fleshless, and unearthly body.
Set deep in the broad shoulders, the flaming visage peered down at the night elves. That it most resembled a brooding skull with huge, curled horns did nothing to dissuade the Highborne that here was a heavenly messenger sent to aid them in their dream of a perfect paradise.
“Know that I am the servant of your god…” he hissed, the flames that were his eyes flashing hot whenever he spoke. “Come to help you open the way for his host and his mostglorious self!
One of the beasts howled, but a snap of the whip sent lightning crackling over the creature, instantly silencing it.
“I am the Houndmaster…” the massive, skeletal knight continued, fiery gaze fixing most upon the kneeling counselor. “I am Hakkar…”
In the space of only a few scant hours, hundreds of the celestial host had poured through.
Mannoroth had immediately taken control of them, sending them out to purge the unfit. Once, Xavius might have found that idea horrific, but he now fully embraced the ways and methods of Sargeras. The god knew best how to achieve the perfect paradise the counselor sought. Had not the quarter reserved for the homes of the Highborne been completely spared? From those who served the palace would arise the new Golden Age of the night elf race, an era eclipsing any existing prior to it.
Or join the resistance and fight the demons, which they had no interest in, unlike the rest of the Night Elves.
World of Warcraft Chronicle: Volume I, Pages 99-100:
Azshara and her Highborne used the Well of Eternity's energies to bring the Legion's minions into Azeroth. Waves of demonic warriors flooded out from the queen's palace, murdering every night elf in their path save for their Highborne allies.
World of Warcraft Chronicle: Volume I, Pages 103-104:
As battles raged across central Kalimdor, one group of Azshara's servants grew increasingly concerned for their own future. This small sect of Highborne sorcerers acted as an extension of the queen's will. From their headquarters in Suramar, they engaged in covert activities aimed at securing Azshara's rule and strengthening the empire.
Though Suramar’s elite Highborne had pledged their undying loyalty to Azshara, their views on the queen began to shift as the war dragged on. The group’s leader, Grand Magistrix Elisande, feared that the Legion did not have the Highborne’s best interest in mind
the rebellious Highborne had no plans to join the night elf resistance and continue fighting the Legion. Fearing calamity, Elisande and her followers worked to fortify their holdings in Suramar.
I’m referred to a voice line from an Island Expedition NPC representing the Horde Nightborne. I don’t know what you’re talking about.