I was doing this quest and completed a harrowstorm by it which completed a daily as well as a daily endeavor. Then, when completing the quest with the pale vampire, got the boss down to about 0.5% and got kicked to login screen. When I relogged, the harrowstorm quest and daily endeavor were no longer completed, so it rolled back at least 5 minutes or so. A few in zone said it happened to them as well, and now, about a half hour later, a guild member mentioned it just happened to her while completing the quest with the pale vampire.
No harm done 'cause it didn't take long to redo them, but I wanted to get it reported.