While this personally benefited me in finishing Casting a Long Shadow, I figured I should report it. With the crazy DPS these days you can essentially one shot Tserrina in ToFS and break her script, bypassing the need for 6 people. You receive the quest update saying you were successful while she warps around the room acting like she's attacking you (but causing no damage).
Actually, I changed it to stop folks from getting stuck on her in older content quests. I thought I called it out in update notes but looks like I didn't so I apologize for that!
Wonderful! Thanks! She was still acting really weird after 'killing' her. She would kinda warp around the room kinda chasing you and doing her casting animation and the portals were spawning shadows, but no damage being done. A little odd.