Here’s a video on my thrall disappearing against the Croc Boss near the Priest King’s Retreat:
Sorry for the poor audio/dialogue. My intention was not to show everyone how much of a moron I am… oh well. 
This was done on a PvE server to check if it was only happening in my SP game. The last time this happened in SP my thrall was knocked into the water like in this video. I, however, do not remember the 3 previous times whether or not my thrall disappeared after getting knocked into the water, despite what I say in the video.
On a positive note. The Croc boss does not seem to get stuck after attacking and ending up in the water like it used to. Good job on this issue Funcom!