Guild Wars 2

Under normal circumstances, in Arah P4 after Simin reaches 50% health she would stealth and regen health slowly until she was re-summoned by the sparks, when she could then be damaged again until the next time she stealths. However, despite many attempts, each time she drops to 50% health Simin would stealth again and regen. I am aware that this is supposed to happen in the first phase, but Simin would stealth and regenerate at 50% health each try, resulting in a never-ending fight in which she would not be able to drop below half health.

My group tried to “reset” Simin by getting out of combat and restarting the fight, yet this bug continued until we eventually gave up and had to restart the instance. I’ve looked on the forums, and one of the previous devs. has already acknowledged this as a bug a year ago. Please fix; I understand that the devs. have a lot to work on, but this has been acknowledged over a year ago and still has not been fixed.

After she goes invisible, you have 45 seconds or so to pull sparks AND damage Simin before she stealths again. If you fail to damage her more than she healed during this time, she will end up back in the first phase.

So your group was probably just slow, and needs to work on pulling sparks faster.

No, "The seer path may also bug at the fight with Simi, the priestess of Dwayna. When this happens, she will hide every time her health reaches 50%, regardless of time spent gathering the sparks or fighting her. " – quoted from the wiki

http://wiki.guildwars2.com/wiki/The_Ruined_City_of_Arah_%28explorable%29#Seer_path_.28Path_4.29

My group has done this twice now, two separate occasions, and both times no matter what we do she bugs out at 50%, no matter how we’re statted or what we’re doing. We’ve followed every idea and there’s just no way to get past this. It’s really off putting.