Math disagrees. Debuffs require application time for each mob, draw aggro, and outside of -resist and -regen, arent very impactful at +4 content. The purple patch hits them disproportionately harder than buffs. At +0, Darkest Night floors to hit, and compares decent to the various defense shields. At +5, you may as well have taken maneuvers. If you understand how the mechanics work rather than going with your gut "feels" this really isnt up for debate.
A portion of certain defenders/corrupters debuffs (-defense, -tohit, recharge, and -speed) need to be unresistable to fix this. Debuffs to damage, resist and regen (due to the massive numbers) are fine.