The Placeholder position is not in sync with the Entry's Text, it is always top-left aligned.

Here's a quick screenshot of what happens when the RadEntry is larger than the default.

This has the side effect of not being aligned with the Text.

Suggested Solution

There are several ways I can think of to approach this, but I think the easiest way would be to just bind the top level control's VerticalTextAlignment property value on the internal Label being used for the Placeholder

<telerik:RadEntry Placeholder="Name"
                              WidthRequest="280"
                              HeightRequest="100"
                              VerticalTextAlignment="End"/>