Arduino Network causing severe battery drain on WiFi connected devices.

Using Arduino Networking, Protocols, and Devices
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I really wish there was a way to fix the Arduino side of this.

I do not see where the library code is involved with an ARP broadcast. I still believe that is accomplished by the firmware in the w5100.

You can check. The library code from Wiznet and Arduino is available as source code in your IDE.
/libraries/Ethernet/
and
/libraries/Ethernet/utility/