So, what is the pont of the battle with Calder?

[Tzardok]

In 1296 she even says "It took all six of us working together to take [Calder's] operation down", implying that working together wasn't the normal.

I don't see how that sentence implies that they don't usually work together. It's simply a statement in Calder's power that it required six high level, near epic characters to defeat him and his cult.