Slow Azure Backup

I can see plenty of other related posts but thought I'd try again regardless. I'm seeing very slow backups across various sites. 

At one particular site, we 100Mbps internet connectivity (so I know it isn't bandwidth related).  The current backup started at 25/04/2016 1900 and hasn't completed as of 27/04/2016 10:38 - it has only transferred 3.60GB of data and just reached the verifying backup stage about an hour ago. We are running Microsoft Azure Recovery Services Agent v2.0.9032.0.

The C:\Program Files\Microsoft Azure Recovery Services Agent\Temp\CBEngineCurr.errlog log is littered with either 
06801A18 04/2709:37:04.38171dscontext.cpp(157)[000000001F334C90]0B8FFF95-3756-4346-A43F-2B230D17C33AWARNINGLast completed state for Ds Id (1668759616) is 7
06802B54 04/2709:37:05.43175OMUtils.cs(72)24239EA1-6E02-4D82-854F-04084C4D6FDD NORMALGetFQDNForServer = host.domain.name
or
06802FC4 04/2707:23:57.27475OMUtils.cs(72)6B5EC526-3D44-4888-A0F4-80E35EAE5BFB NORMALGetFQDNForServer = host.domain.name
06801A18 04/2707:23:57.80971dscontext.cpp(157)[000000001F334C90]0B8FFF95-3756-4346-A43F-2B230D17C33AWARNINGLast completed state for Ds Id (1668759616) is 5

I'm often seeing this blamed on Anti-Virus - I can confirm System Center Endpoint Protection IS installed, the C:\Program Files\Microsoft Azure Recovery Services Agent folder has been excluded from scans, the C:\Program Files\Microsoft Azure Recovery Services Agent\bin\cbengine.exe process has also been added as an exception.

The steps at https://support.microsoft.com/en-gb/kb/3090067 have been performed and haven't helped. We are backing up just over 950,000 files. 827GB.

Any help is appreciated.