Q1 2014 will bring responsive capabilities for the RadTileList control, so I advise that you wait a couple of weeks until it goes live and test it. Support for size set in percent will be introduced, and the control will automatically calculate the number of rows it can use.
At present, the rtlistScrollWrapper element has its width calculated according to the number of tiles and the tile column width, which is 320px plus a little margins/paddings. Having other tile dimensions is not supported at the moment.
On the rtlistWrapper class - this is an element that creates the separate columns of tiles and it is supposed to be 320px wide - this is the width of a wide tile plus some margins. The issue, however, is, that all your tiles end up in the same wrapper element, which should not be the case. I have just tried the wrapping elements are created accordingly. Can you confirm you are using the Q3 2013 SP1 version? Can you confirm you are following the guidance from the following resources:
If you share with me some code that leads to the problem, perhaps I will be able to help with the current version of the control. Without being able to examine the exact case, this would be much harder, however. You could replace databinding with a loop that will create tiles for each group in the code-behind.
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