Debuff are not op, they are good, but not op. The thing that make them too strong are just 2 things: Azrael borg and azrael's torment.
Almost everybody are using those cores. But those cores aren't only good for using debuffs, they also counter other kinds of builds.
Like supports mercenary with blood commander. Supports builds using infernal surge or any other build with feast of flesh. Those 2 azrael cores, make infernal surge and feast of flesh almost useless. You waste a turn getting a buff and your opponent just reduces it to nothing while also deals damage.
Azrael borg: as being an unlimited core I would increase it's special CD from 4 to 5. Reduced it's effect from 75% to 50%.
CD should be increased since you can spam smoke/malf and azrael all along the battle, way too strong. Effect should be nerfed since you are not wasting energy.
Azrael's torment: Increase energy cost from 125 to 150. Stay the effect in 70%.
This core is being used too much, with a small nerf it should be a little less usefull. Efect must stay in the same way since you are wasting energy and is not unlimited.