Until this behavior is fixed as a workaround you can use InvokeProcess Activity to start the ArtOfTest.Runner.exe on the build server. More information you can find using the following link:

https://msdn.microsoft.com/en-us/library/gg265783(v=vs.100).aspx#Activity_InvokeProcess

You can create a batch file containing for example the following command:

cmd.exe /c C:\"Program Files (x86)"\Telerik\"Test Studio"\Bin\ArtOfTest.Runner.exe list="PathToTheTestList"

if %ERRORLEVEL% GEQ 1 EXIT /B 1 

Where the last line will transform any different result from 0 to return 1 as an exit code.

You then change the Build Process Template as explained in the following article:

http://www.ewaldhofman.nl/post/2010/11/09/Part-15-Fail-a-build-based-on-the-exit-code-of-a-console-application.aspx

Thank you for your understanding and patience.