I have read similar posts regarding this issue but they were mainly on Windows 7 or XP machines and older browsers.
I have installed Windows 10 64 Bit Pro as a Virtual Machine in VMware Fusion 8.5 on a mid 2010 3.2Ghz i3 iMac with 8Gb ram running on Mac OSX Sierra.
The VM has been configured with 4Gb ram and 1 core. VMware tools have been installed.
The customer is complaining of painfully slow internet browsing both with Firefox and Edge in Windows 10 yet on the iMac in Safari its quick. He has a 15 mbps Broadband so I don't believe this is the problem.
Can anyone recommend any settings or tweaks that may improve browsing speeds. From what I can ascertain its not just slow searches but result pages open very slowly too. Would assigning more cores to the VM improve things. I think most modern browsers are multithreaded but don't think either browser is optimised for multicore.
Just plucking at straws could it be a network issue possibly slow DNS resolution??
Could be DNS, you'd want to do some isolation and troubleshooting to figure that out.
A quick sort of test could be done by taking a busy webpage that takes a while to load, save it and run it locally. If it chunks, it's a browser load thing and consider adding another CPU core to the VM. If it runs quickly, likely a DNS thing, or at the very least potentially some other networking issue.
Try toggling between NAT and Bridged if that's the case.
Also, pay attention to the system loads at the time. So, what's the Host CPU doing, what processes are using it? What about Disk I/O... 2010 was a LONG time ago and hard drives were REALLY slow back then, and that used to be the #1 bottleneck for running 2 OS's on simultaneously.
Likewise, correlate the Host operations with Guest activity. So use Task Manager in Windows to see what CPU usage looks like, what Disk I/O looks like, and compare that with the host.
If Windows is pegged at 100% and the vmware-vmx process is also at 100%, you are having an issue with a lack of CPU resources in the VM. (i.e. the VM wants 1000%, we can only give it 100%, but you should have an additional core to offer the VM to take it to at least 200%)
Hope that helps!