I know a fellow SMN already submitted a bug report about this before the patch and it hasn't been adressed sooo... here:
Currently because of the way cover works, it can make fester hit for 0 damage and miss an aethertrail stack. It's a very big dps loss for a SMN and I am baffled by the fact this issue has been adressed in PVE but not PVP.
Either give fester the PVE treatment or make it connect to the current target, even if the damage is redirected to the PLD.