Hi Ade,
I read through your case in our database. Here are a couple more suggestions/questions that I didn't see requested in the case:
1. What happens when you perform a backup of just system state on the servers? What happens if you run a backup job without backing the system state on any of the servers? How fast does it run then?
2. On the one job that backed up successfully, but was 17 hours slow, if you look through the job log, where are the slow points? Do they occur when it hits the system state on all the servers?
3. Are you using AOFO, and have you tried running a backup of system state without AOFO checked? Please try that and reply back with the results.
At this point, even though I think my questions above are valid and need to be taken a look at, my best advice to you since you have a case history with us, would be to call back into Support and request for this case to be reopened and escalated to an Advanced Team technician.
If you do not call back in, please let me know if you can answer the questions above. Even with those answers though, I have a feeling a more thorough investigation with debugs, sgmon logs, and other logs would need to take place.
Thanks.