There’s only 6 bleeders in the game who have more than 1000 attack at level 26, Hydraboa, Nantem, Scorpius Rex, Scorpius Rex Gen 3, Suchotator and Spinotahraptor.
We have 4 uniques in total which are bleeders which are Pterovexus, Scorpius Rex Gen 3, Spinoconstrictor and Stygidaryx. Are Pterovexus and Stygidaryx worth using in this arena currently, no is the short answer.
My optimal buffs for Stygidaryx would be to give it Stun and Slow Immunity along with its raid moves such as Scratching Resilient Rampage, you would not need to give it a damage buff in this case either.
For Pterovexus change Distracting Impact for Revenge Distract Impact and increase its attack to 1350, the same as Monomimus.
Spinoconstrictor needs only really a resistance tweak, giving it 67% stun resistance and full decel immunity should see it played more higher up, especially since it’s made of exclusive components.