You can easily ride out Festergut's 3rd inhale with proper CD management.
Originally Posted by Phantomx16
Watch for him to cast the 3rd inhale, 1 sec before it finishes casting hit your Last Stand and Enrage Regeneration. 1 sec before Last Stand ends hit Shield Wall. If done right you should be covered for the whole time without a risk of death. If you mess up the timing a on use like the one form the Key or Satrina's will help.
But to your original question I would ues the Key over the Coin in the majority of situations. The coin is more situational but still good to have.
There is something so appealing about backhanding someone across the face with a shield.