Thanks furry.
I replied back to the D-Track (ticket) with everyone's information. Seems like the write speed is capping at 7MB/s and get bursts at 27MB/s. Sounds like a limitation but they will check with the vendor.
Remember the router is not going to be as powerful as a PC or dedicated NAS. The router has to process a lot and I am assuming the USB ports are low priority. The router has to inspect incoming/outgoing traffic, routing, NAT, encryption, WIFI, Ethernet, rules, etc. So it could be a lack of memory/processing power that is slowing it down.
I wonder if connecting 1 PC to the router without internet or anything else connected with smart connect off if "write" speeds would be better. If not sounds like a chipset/firmware limitation.