I have a 2014 iMac with gigabit, I also have a xfinity modem that is also gigabit. my write speed according to blackmagicdesign disk speed test is 11.9 mb/s write and 12.5 mb/s read. those numbers seem very slow to me. anything I can do to speed things up?
Are you able to try using the drive with a static ip?
Also make sure that all the Ethernet cables are gigabit compatible.
Is the connection between the Mac and the EX4 via a switch or a router? Routers will be slower as opposed to switches. In switches you generally get what you pay for. The less traffic on the same subnet the better. If you can setup a VLAN between the Mac and the NAS so much the better.
Bottom line though is you don’t buy these things for performance, but for convenience, for convenience and good software. If you want performance, go with Thunderbolt from your Mac and perhaps even a Thunderbolt NAS.