When Public test relam came out they made it so all eth items lost durability while using echoing strike.
Now that the PTR is over, blizzard posted the newest patch notes. In the notes blizzard posted...
Quote
Developer’s Note: Based off feedback from the PTR, we took another look at the decision to fix the bug for durability loss on echoing strike. While it was a bug, the feedback made us re-examine the impact to player's decisions around weapon choices. After discussions, we decided to revert the fix as the impact supported the intended fantasy of the skill while still fitting generally within the original vision.