you can't simply pick two points in time and then get reasonable results regarding trends. Day to day variance is just too big to conclude anything from just two datapoints.
There are also lots of factors to consider besides amount of datapoints, like time of the day, events happening (during Raids more PvE chars will be logged in for example), etc...
Also even just looking at the two datapoints the evaluation seems off. In the left screenshot there are about 20% more bonedancers than skald, in the right they are about equal. So either skaldpop has increased or BD pop has decreased. None of the classes is marked as changed though.
Surprised how low Warden is on the list considering it was my main class on live....Not so surprised that Scouts aren't even listed on the more recent numbers, considering how broken it is.