I've noticed the geocoder widget uses a hard-coded "singleLine" parameter for locator service. That works fine with the default Esri global locator, because it happens to accept "singleLine". However, almost every locator built out of ArcGIS uses "Single Line Input", three words spelled out with space in between. That makes the geocoder widget not suitable for many locators. I would assume the widget would at least query the locator meta data the first time and then send the parameters the locator are expecting, but in this case, it seems was forgotten?