Okay I guess after a firmware reset I lost openssh-client . I reinstalled that and scp and rsync is back to 1.2MB/s without VPN and 500KB/s through VPN.
Didn’t realize how much faster openssh is over dropbear on these little routers!
Nope it was dropbear causing the bad performance. OpenSSH is much faster. As noted in first post reading over the network via curl (http) I was writing to the USB device at 1750KBps.
Using DD I tested write performance to the USB device to be 2.7MBps .