Cookie0810

We do have than in Win 10 for fonts installed by the user. I'll keep looking around but struggling to find someone who has experienced the same issue!

It's been a known issue for a while. AFAIK, they haven't fixed it yet. 
 
I found that if you set the download limit in the Battlenet launcher to 100Kb/s, let it download for a bit, then set it to 0Kb/s (unlimited), it will download at full speed for a while, then you'll have to repeat the process. 
 
EDIT: If you have a VPN, try connecting to an NA server and downloading through the VPN. I've heard some people in the UK have had luck with that. 

Honestly, if it is in warranty I'd say just contact them and see what they say.
 
If it isn't a new thermal paste job will probably help to some degree. Also clearing out any dust while you are in there too would help.

I remember having this same issue some time back. From what I could figure out the program isn't a thing anymore, although I'm sure there is a way to get it installed and working that I am just not aware of. 
 
Please remember I could be wrong but that is what I can remember.