Slow pbpaste / pbcopy
Consider reporting this directly to Apple via bug reporter as it is unlikely anyone here will be able to help.

Delays of around point zero one less than one second are probably acceptable to Apple's engineers. 100% CPU is also acceptable; useful work is being done for the user when copying and pasting.

The pasteboard is not designed as a performance focused transport mechanism for processes and scripts.

Pasteboard operations can result in a cascade of notifications to processes. This is likely what you are detecting as notifyd is responsible for system wide notification delivery. This behaviour is normal.