This shard should reduce damage by 15%, it does nothing.
That has been a known issue since the Trials patch, it actually makes you take more damage. A fix is going in today with the 0.3 patch that should make it work correctly.
yeah I knew it was, but when I searched for the bug I couldn't find it and started freeking out that it would be missed.
Though the tool tip is a bit confusing now . but its obvious at least what it means.