In such operations as housekeeping, backups, stats run, etc... I think the bottlenecks are more at the database level than in the processors.
So if you add more processors around already overstressed databases I am not as sure as you are that things will improve. Remember that WCG DBs are in terabytes and that everything has not been switched to a clean Boinc-only setup yet.

As far as we can see here or in our own clients the critical part of WCG (i.e. sending WUs to clients and collecting them back timely) is usually running fine even during those operations. It is some of our "human" transactions which are affected during these sessions, but these transactions are not essential for the process, to say the least.

Cheers. Jean.