Example: I am in a random MoP group and we are in the middle of the fight and everything stops. I have seen it as bad as my DOT timer for SW:P goes to negative 30 seconds. Then everything catches up all at once. This is very frustrating because Im sure it looks like I am just standing around the whole fight.
When I am questing there is zero issue. When I am groups with other people in the regular world, I have zero issue. No one else in my guild is experiencing anything like this, or else I would say the instance servers were just overloaded.
This began with the MoP patch and was MOST prevelant when I was doing the Theramore scenario. Regular dungeons were perfect.