Hello @Woidyla
I actually use the Pulse VPN for my employer as well, and I'm on Comcast. I have 400Mbps service, and I just ran a speed test with Pulse VPN connected and without. Without the VPN connected, I got over 450Mbps down and 11Mbps up, while with VPN connected, I got about 350Mbps down and 10Mbps up. So, I am seeing an impact, but it's nowhere near as bad as what you are seeing. I have Google WiFi rather than Nest WiFi, but I don't think that is making a difference here.
I just have a simple cable modem, though – can I ask whether you have a combination modem+router from Comcast? If so, the "double NAT" issue may be causing this problem for you. Specifically, I wonder whether path MTU (maximum transmission unit) discovery is breaking due to the VPN encapsulating full-size packets inside another packet, and the control packets used to discover the smaller MTU aren't getting through both layers of firewall.
If you have a combination modem+router, and you can configure it to be in "bridge" mode, that might be worth a try.
If that's not possible, it might be possible to configure your system to use a slightly smaller MTU that leaves enough room for the VPN wrapper. Something like 1460 bytes instead of the default 1500 bytes? Or maybe even smaller – like 1400 bytes to start with, just to prove whether this is the issue or not, and then you can bump it up from there to figure out where the breakpoint is.
