It has been tested and proven in several cases that +CHR makes the debuffs stick. As you get to higher levels (I believe Heziki is 75 now) you need more +CHR. It's kinda proportional to your base. Why would a BRD want to trade his precious CHR for an extra 2.5 on requiem? Or maybe a tiny bit on elegy? Personally I would rather do anything to keep the songs landing.