yup, did include all the loading and requiring settings. i slightly had to change the Ux.locale.Manager.setConfig({ and Ux.locale.Manager.init section:
this is my app.js:
Code:
Ext.Loader.setConfig({
    enabled : true,
    paths   : {
        Ux : 'Ux',
        'Ext': 'sdk/src'
    }
});


Ext.application({
    name: 'myeasterapp',


    requires: [
        'Ux.locale.Manager',
        'Ux.locale.override.st.Component',
        'Ux.locale.override.st.Button',
        'Ux.locale.override.st.Container',
        'Ux.locale.override.st.TitleBar',
        'Ux.locale.override.st.field.Field'
    ],


    views: [
        'Main',
        'Contact',
        'Status',
        'Settings'
    ],


    models: [
        'Contact',
        'Status'
    ],


    stores: [
        'Contacts',
        'Status'
    ],
    
    phoneStartupScreen: 'resources/loading/Homescreen.jpg',
    tabletStartupScreen: 'resources/loading/Homescreen~ipad.jpg',


    launch: function() {


        // Initialize the main view
        Ext.Viewport.add(Ext.create('myeasterapp.view.Main'));


        
        Ux.locale.Manager.setConfig({
            ajaxConfig : {
                method : 'GET'
            },
            language   : 'de',
            tpl        : 'locales/{locale}.json',


            type       : 'ajax'
        });
        Ux.locale.Manager.init();
        
    }
});
well, in dev mode this works just fine like that...