Isolated Gate Driver Consistent Failure
As winny pointed out, the minimum voltage on the gate pin is -0.3V per the datasheet. My scope was showing an undershoot of ~1V for a brief time so I was violating the device specifications. 

Upon changing the sinking resistor from 1 Ohm to 2 Ohms, and adding low capacitance Schottky diodes from source to gate, the undershoot disappeared and my gate driver operated successfully for over 30 minutes where previously it would die within 1 minute.