In Suramar we have G[43309]='K1100 L110 A:700722 T:700416 P:T74358999+U74442900 E21570'
for the Quest The Perfect opportunity.
This translates to

Nightfallen Rep: Honored +8000
and
Arcane Thirst Thalyssra: stable

Although she is at (13/100) stable, this check isn't fulfilled and the quest therefore "unavailable"

[10:19:26]Dump: value=GetFriendshipReputation("target")
[10:19:26][1]=1860,
[10:19:26][2]=113,
[10:19:26][3]=42000,
[10:19:26][4]="Arcane Thirst (Thalyssra)",
[10:19:26][5]="First Arcanist Thalyssra is Stable.\r
\r
The nightborne have an insatiable thirst for |Ancient Mana|r, which can be found all over Suramar.",
[10:19:26][6]=1391545,
[10:19:26][7]="Stable",
[10:19:26][8]=100,
[10:19:26][9]=200

@smaitch what might be going on there?