I've met quite a few vamps, both in arena and fjord, and sometimes when they're using their Charmed Strike, I cant move/cast a skill/anything for like 5-8seconds.
When this happens, there are no debuffs that can be seen in my right corner, and I know from experience I'm not the only one who's felt this bug/typo, had my teammate in arena mention this yday aswell.
So imo, we now have to possible options:
1. There is a bug with the Charmed Strike.
2. The tooltips are wrong, so it is not written that the Charmed Strike got a chance to fully cc a target for 5-8seconds.