Finally Microsoft published article about problems with iOS 6.1 and Microsoft Exchange Server.
When user with mobile devices with iOS 6.1 syncs mailbox Microsoft Exchange Server resources are consumed, transaction logs growth becomes excessive, memory and CPU use may increase significantly,a nd server performance is affected.
You can read about it here:
Right now, Apple and Microsoft are investigating this issue. When they find any fix, it will be published as soon as it will becomes available.
If you have such problems in your Exchange environment you should open case with Apple Support.
Now Microsoft recommend only Workarounds: