Thanks for your query. We are unable to observe any decrease in performance. We will further look into it. Meanwhile can you kindly create jsfiddle with the code that you are using and share the following info so that we can properly look into it.
1. OS details (Name and version)
2. Browser details (Name and version)
3. Zoom-level/panning at which you find performance issue.
Thank you for your quick answer.
It is not easy to share my code because I have a complex server back-end.
1. OS = Windows 7 x64
2. Browser = Google Chrome version 52.0.2743.116 m
3. Actually the problem happens when I put the mouse over data point of the series, then if the legend is displayed and then I pan, it is slower than if I pan without putting the mouse over a given data point. It seems that the problem also existed with the version 1.8.0 but it is a little bit faster.