debuffing isnt effective because the easier route for ally content is to go bard rotation, people take what they get once brd/cor rotation would get nerfed. trust me. And yes I know blu debuffs dont mostly stick, some however do. And the rotation nerf would give an incentiv to fix those blu debuffs without makeing the game broken.
Debuffing works, just noone does it, because rotation buffing requires less/no work and just a couple of mules. even if potent debuffs are 2/3 of the time up, they still would help alot.