Indeed this is a pretty old thread and back in the days using dock was the only way to achieve a proper "grid" layout. Most common cause of spacer rows is improper or missing top/bottom alignment of report items. Make sure the top and bottom edges of all report items line up with one another. The alignment and applying the same height to report items will usually solve the problem.
About the problem with Docking="Fill", most likely the order of the TextBoxes in the items collection is not correct. In other words, when docking, the order of the items in the collection of the item they are added to/docked into is taken into account.
Anyway since Q1 2009
when you aim for a tabular layout in Telerik Report, we highly recommend using the Table
item, which has been created for this very purpose. Using the Table item guarantees that the columns and rows would be consistent and everything would fit in the respective table/excel cell.
All the best,
the Telerik team