public class ArrowDependencyViewModel : BaseViewModel
{		
	Point start;
	Point end;

	public ArrowDependencyViewModel()
	{
	}

	public Point ArrowStart
	{
		get { return start; }
		set
		{
			start = value;
			NotifyPropertyChanged("ArrowStart");
		}
	}

	public Point ArrowEnd
	{
		get { return end; }
		set
		{
			end = value;
			NotifyPropertyChanged("ArrowEnd");
		}
	}
}

public abstract class BaseViewModel : INotifyPropertyChanged
{
	public event PropertyChangedEventHandler PropertyChanged;
	
	protected void NotifyPropertyChanged(String info)
	{
		if (PropertyChanged != null)
		{
			PropertyChanged(this, new PropertyChangedEventArgs(info));
		}
	}
}

<UserControl x:Class="Arrow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

    <Canvas>
        <Line x:Name="Cap">
            <Line.RenderTransform>
                <RotateTransform x:Name="CapRotateTransform" />
            </Line.RenderTransform>
        </Line>
        <Line x:Name="Connector" />
        <Line x:Name="Foot">
            <Line.RenderTransform>
                <RotateTransform x:Name="FootRotateTransform" />
            </Line.RenderTransform>
        </Line>
    </Canvas>
</UserControl>

public partial class Arrow : UserControl
{
	Point startPoint;
	Point endPoint;

	public static readonly DependencyProperty StartPointProperty = DependencyProperty.Register
		(
			"StartPoint",
			typeof(Point),
			typeof(Arrow),
			new PropertyMetadata(new Point())
		);

	public Point StartPoint
	{
		get { return startPoint; }
		set
		{
			startPoint = value;
			Update();
		}
	}

	public static readonly DependencyProperty EndPointProperty = DependencyProperty.Register
		(
			"EndPoint",
			typeof(Point),
			typeof(Arrow),
			new PropertyMetadata(new Point())
		);

	public Point EndPoint
	{
		get { return endPoint; }
		set
		{
			endPoint = value;
			Update();
		}
	}

	public Arrow()
	{
		InitializeComponent();
	}

	private void Update()
	{
		//Тут обновляются Cap, Connector и Foot согласно полученым точкам
	}
}

<ItemsControl ItemsSource="{Binding ArrowDependencies}">
	<ItemsControl.ItemTemplate>
		<DataTemplate>
			<local:Arrow StartPoint="{Binding ArrowStart}"
					  EndPoint="{Binding ArrowEnd}">
			</local:Arrow>
			
			<!--Если раскомментить этот код и закомментить local:Arrow то привязка работает нормально-->
			<!--<Path StrokeThickness="3" 
				  StrokeStartLineCap="Round" 
				  StrokeEndLineCap="Triangle" 
				  Stroke="Red">
				<Path.Data>
					<LineGeometry StartPoint="{Binding ArrowStart}" EndPoint="{Binding ArrowEnd}"/>
				</Path.Data>
			</Path>-->
		</DataTemplate>
	</ItemsControl.ItemTemplate>

	<ItemsControl.ItemsPanel>
		<ItemsPanelTemplate>
			<Canvas />
		</ItemsPanelTemplate>
	</ItemsControl.ItemsPanel>
</ItemsControl>