Using the power of the Roseus tree, Quinn was able to coordinate the marked beasts to help out the Cursed faction in holding off the enemy. However, at the end of the day, they were just beasts, whereas nearly all of the enemy forces consisted of vampires who had access to super strength, great speed and blood powers.
It also didn't help that thanks to a certain family that had been on the island for a while now the strongest beasts that the tree had been able to mark were at the King tier. Quinn could use the power of the tree to make them somewhat stronger but even that could only do so much against their foes' teamwork.
Then there were also the stronger vampires who were able to ignore the beasts in the jungle and were heading straight towards the Demon tier beast. It was the second line of defence's job to intercept them.