There seems to be a new problem with the kills of the Prophet Tharon'ja in Drak'Tharon Keep. For now, the number of kills for DTK is being removed.
Now the game appears to give you credit for three kills instead of just one. I've noticed this on several of my own characters now and it appears to be a common problem.
Until this is fixed, if that's even possible to retroactively correct this particular stat, I can't guarantee the accuracy of your Drak'Tharon Keep boss kill numbers.