There are no known AV exclusions necessary, from my search around the KBs.
To try to address performance issues during initial encryption, I'd recommend the following:
- Minimise the amount of data on the drive
- Make sure it is healthy (no bad blocks, etc.)
- Defragment the drive
- If possible, untick the "Encrypt unused disk space" option (only recommended for brand new drives that have never seen any data of any sort, and have just been installed with a fresh build)