How to load template in angular after controller finishes loading parameters?

There are a number of things you could do.

You could hide the empty blocks, and only show them when the data has loaded:

app.controller('mainDashboardApi', ['$scope', '$http',
    function($scope, $http) {
        $scope.isLoading = true;

        $http.get('api/dashboard/main').success(function(data) {
            $scope.dashboard = data;
            $scope.isLoading = false;
        });
    }
]);

That would be the manual way.

But ui.router supports this sort of scenario (as does ngRoute) with a resolve parameter of a state, where you could delay loading a view until all the promises are resolved (or one of the is rejected):

$stateProvider
    .state('dashboard', {
        url: "/dashboard",
        templateUrl: "dashboard",
        controller: 'mainDashboardApi',
        resolve: {
          dashboard: function($http){
             return $http.get('api/dashboard/main')
                      .then(function(response){
                         return response.data;
                      })'
          }
        }
    })

Then, dashboard could be injected (like you would other services) into mainDashboardApi controller:

app.controller('mainDashboardApi', ['$scope', 'dashboard',
    function($scope, dashboard) {
        $scope.dashboard = dashboard;
    }
]);