Same Problem here, narrowed it also down to the _scrollTo of the Grid.(and the inner native browser functions)
The event of measuring is on cell click by opening CustomEditor with KendoComboBox
Same grid, IE11 latest => ~300ms, Chrome 39 => ~4ms <> 100xTIMES slower just to see input after click with custom editor!
Only 300 records. So sample from above doesn't apply.
On enterprise behalf here we can't change the browser (policy, security).. KendoGrid seems to be a future show stopper.
Update to IE11 from IE9 was a big deal. Please consider to think about redesign, use own or alternative functions of the performance killers. New software with Kendo, which is slow than ASP.NET Controls (Telerik JS Client Code) won't be accepted by business users.
Hopefully someone finds a workaround to this...
Kind regards, Otto.