Guild Wars 2

Hello Guild Wars 2 Forums!
Im not sure whether this is a bug or an actual feature of the dungeon but after having quite a few runs of Arah Exp. P4 fail because we cant get Dwayna below 50% health I thought this cant be the way its supposed to be. I know there are many threads like this already but I didnt really get anywhere from what I found. Everyone has a different opinion about this and while the wiki says it would be a bug many say it isnt and its an actual feature of the game. Which is really confusing.
If you have any idea what is behind this odd behavior of Dwayna please tell me!

At 50% health and below she will go into stealth wich heals her. The stealth has a short cooldown of 45 seconds.To get her out you need to put the 5 sparks back in the center. after this the 45 second countdown start. If you don’t deal enough DPS to damage her more then the amount of health she gains during stealth you will never get her down or even below 50%.

This is often called the bug described on the wiki. I don’t know bout the bug, but I personally have never witnessed it. I have seen the effect described above. Many times, using some damage booster was enough to get the ball rolling till she was down.