SQL Server query across several linked servers - abysmal performance
The poor performance is because you are using linked server.  There is a constant difference of opinion between developers and database admins.  Database admins know linked server connections are slow.  Developers want them because they solve problems for them.  I have been both a developer and a database administrator and I remember as a developer, I pushed to get linked server added.  As a database admin for the past 20 years, I have trouble shot poor performance thousands of times to find a linked server connection is the cause.

Use transactional replication to get real time data to your report server.  This will eliminate the 24 hour delay and it will eliminate your need to use linked server.  You will also have a performance gain on your source servers because read only report queries won't be competing with live transactions that run your company.