After the last patch it seems as if the sounds and damage numbers in the scrolling combat text has gotten out of sync. Sometimes the scrolling combat text doesnt keep up with all the 10 channels anymore, and it goes for the sound of the attack as well. I got worried that you were missing attacks, even on static targets such as the dummies in the mists, but when doing extensive testing it seems that all of the 10 channels indeed registers in the combat log and that is just an issue with the effects.
Its highly annoying though and now I wonder if anyone else has experienced similar problems since the last patch.