So the only reason to replay memories is to just indulge your masochistic fetishes of fighting obnoxious enemies over and over? There is no tangible benefit for repeating the fights?Unfortunately, no. You won't earn Memory items from re-fighting bosses at the Sculptor's Idol; you only get them on a new NG+ cycle. There's also a special item broken into three parts; if you get all of them, you can trade 5 skill points for an attack increase, but I don't recommend it until you have all the skills unlocked.
If you die there, does it count towards accumulating dragonrot?