Delay that happens inside RadChart could be caused by loading a lot of data (like thousands of data points), having a large resolution for the chart image, or using computation intensive appearance features such as blurred shadows or complex gradients.
While the product was designed to be easily customizable and feature rich it does not cope well with extremely busy charts or rendering a lot of graphs on a single page. We are continually improving performance as we go but still the bottom line is that the control is targeted for casual situations which do not require a high performance solution. There is a trade off to make between high customization and high performance and we've gone the rich features path as it is what most of our customers are interested in.
Please accept my sincere apologies for the inconvenience caused.
the Telerik team