NetEdit first broadcasts a query for connected devices, then waits a second or two for them to answer. It then cycles through each device that answers and reads all of the general setup data of each. On Host's office network there's 30+ devices and that process takes about three or four seconds total. If Windows networking gums up the works by trying to connect through VPNs and such stuff, we've seen things hang up for a long time. Multiple NICs shouldn't be an issue, but you can use the Network->Adapter menu to choose which NIC to query.
About 90% of what's on our network is Do-more and most are running short programs, which means they will respond very fast. If you are mostly running DL with longer scan times, I'm sure that process is slower, but it seems unlikely that it would be that much slower.
From Task Manager, what does processor load look like? Wondering if something is hogging the CPU.
Once NetEdit is running, if you hit the Scan Network button does it take a super long time too?