If the performance is very bad even when using paging or virtual scrolling, I suspect that you have not enabled server-side data operations, and all the data is downloaded to the client in bulk, which generates a slow Ajax request.
Is the data used by some other widget except the Grid? If not, then the performance is better when the dataSource is not assined to the Grid probably because no data is loaded from the remote service (the Kendo UI DataSource does not request data automatically after it is initialized).
Also, if you are using templates, it makes a difference what these templates contain.
I am not able to provide more specific information at this point, as I don't have enough information.
Generally, the greater the number of columns, the smaller the page size should be, if you want acceptable performance, including rebinding speed. Of course, it also depends what is the exact scenario and how is the Grid configured.
Join us on our journey to create the world's most complete HTML 5 UI Framework - download Kendo UI