Didn't mean the Player Character, but if I'm recalling right, one Female Human participating in the Nazmir operations did ally with the Blood Trolls, even trying to ritualistically sacrifice a Zandalari Troll (don't remember if she actually did that).
The Alliance Player go to Uldir to help Brann destroy G'huun, because it's a World threat. Without G'huun, the Blood Trolls aren't a real menance to anyone outside Zandalar.