It is just another bad take on the story telling and twisting of what we know of other races or have experienced first hand. Every single so called alliance has been massively underwhelming and mainly because of the reasons behind each one and how it slaughters anything established just so it can make Scarlet work.
Flame Legion
The flame legion want to enslave the rest of the Charr and have no respect for females of any race. They kitten and torture female Charr for kicks and you can even read about it in the game after you finish the flame shaman event. Females of other races are seen as something even lower because flame legion are racist on top of being extremely sexist. The flame legion has also suffered setbacks before always rebuilt even it it took time on their own power. Abaddon with the use of the titans was really the only one who successfully manipulated them. They are also highly protective of their magic as even the priory doesn’t truly understand the older magics gifted to them long ago such as the searing cauldrons.
Yet Scarlet a FEMALE of a race seen as very gullible and naive some how managed to get this race to do what she wanted. She got them to teach the dredge their deepest magical secrets, some how got them to follow a female of another race, got them to rely on another race for power when their goal is to enslave the world. She even directed them to split their attack off taking back leadership of the Charr alone and attack the Norn at the exact same time. It made no sense and went against all you know about the flame legion.
Dredge
A highly xenophobic race that was just betrayed by those they see as surface dwellers that steal all their resources and are out to enslave them like the dwarf’s did so long ago. It was just an inquest betrayal but they see all surface dwellers the same. This was rapidly followed by a split in the dredge leadership that you help with the story in SE. So on top of that the dredge are in the middle of a massive civil war with themselves underground. The communist like leadership is fighting the workers for control of their race.
Yet they are willing to listen once again right after that betrayal and during a civil war to yet another outsider with the promise of power so quickly? The workers revolt is nowhere to be seen during all this as well as if all the progress made in Sorrow’s Embrace meant nothing at all.
If anything the xenophobic nature of the dredge would have been enhanced by those recent events. While she might have been able to get the communist side to listen somewhere to her the parts of it trying to grasp power. It is just highly unlikely with recent events that they would do so and even more unlikely they’d do so with a race that views them as future slaves or something to be burned to ash.
Krait
The history of the krait is one of extreme xenophobic nature. They see every other race as less then dirt and one day hope to commit genocide upon each and every one of them. The very few instances the krait actually bothered to talk to anyone in a dialogue such as the human story was only made so they could try to get what they wanted. They manipulated, used illusions, and lied through their teeth until they were caught. So the only time they’ve bothered to speak to anyone they never did it in a meaningful way. It was just a means to an end with hollow words and after being discovered it was right back into the killing. This is also very very rare according to what we know and highly unusual of them at all for any dialogue offered. Their entire history is one of working alone to wipe out all other races.
The krait operated alone at sea from their giant towers full of slaves with these goals and those that saw these towers would flee in fear. Many would not make it and become food/slaves for the krait. Even after losing these towers to something unknown and being driven inland the continue the same practices. So a loss of power did nothing to change the centuries of hate the krait love so dear.
Yet Scarlet not only managed to talk to this race but got them to ally with another and share their ancient magic passed down verbally from one generation to another. Magic they have never shared before to anyone. She also got them to setup shop inland even further from where they are strongest with this other race in a giant tower. All this for shards they see as a key to their ultimate goal. The krait didn’t try to fight Scarlet for them, steal them, nothing. They just went along with it.