This story instance is bugged unfortunately.
The first time I tried it I got to Justicar Adrienne which reached 76% and started rolling around. Bringing down the Unstable Bloodstone Fragment didn't destroy her shield which makes her invulnerable. I destroyed the fragment several times and nothing.
The next tries were even worse - I couldn't get past the Veteran Bloodstone Elementals that are right before Justicar Adrienne. Same problem - destroying those unstable bloodstone fragments doesn't destroy their shields - those fragment respawn after few seconds and nothing happens.
I will keep trying since there is always a glimpse of hope that it will work next time but I just decided to leave it here since there is absolutely something not ok since this thing happened several times and makes it for me impossible to go on with the story.
date, time, and time zone the bug occurred - few minutes before the post
name of map you're on - Bloodstone Fen
your character name, level, race, and profession - Vakh Soulscythe, 80, human reaper
whether you're in a group - nope