The impact of multiple Grandmasters fighting in the church was different from that of the Master ranks fighting on the outside.
The court was fortified, capable of handling the impact of a full-frontal attack of Grandmasters, while on the outside, a sneeze from those people could break a wall.
So what of a fight between a bunch of them?
Well, that didn't actually happen, as the enemies that came out of the foray were mostly low-level. At most, their strength reached the level of Adept.
But that alone was causing enough damage to even Master Rank who had endured some of the weirdest enemies known to man.
They appeared and disappeared on their own, attacking from all directions, always attempting to infect with their blood disease. Though they did leave the mortals alone, the spread was not as dangerous as many might have expected from an attack of this scale.