diff --git a/awx/main/models/inventory.py b/awx/main/models/inventory.py
index 805e4eb1f4..c7b9254ada 100644
--- a/awx/main/models/inventory.py
+++ b/awx/main/models/inventory.py
@@ -247,6 +247,7 @@ class Inventory(CommonModelNameNotUnique, ResourceMixin, RelatedJobsMixin):
 
         data = dict()
         all_group = data.setdefault('all', dict())
+        all_hostnames = set(host.name for host in hosts)
 
         if self.variables_dict:
             all_group['vars'] = self.variables_dict
@@ -264,6 +265,8 @@ class Inventory(CommonModelNameNotUnique, ResourceMixin, RelatedJobsMixin):
             ).values_list('group_id', 'host_id', 'host__name')
             group_hosts_map = {}
             for group_id, host_id, host_name in group_hosts_qs:
+                if host_name not in all_hostnames:
+                    continue  # host might not be in current shard
                 group_hostnames = group_hosts_map.setdefault(group_id, [])
                 group_hostnames.append(host_name)
                 grouped_hosts.add(host_name)
diff --git a/awx/main/models/jobs.py b/awx/main/models/jobs.py
index bb8f6f0dbc..a0ea174bbe 100644
--- a/awx/main/models/jobs.py
+++ b/awx/main/models/jobs.py
@@ -595,6 +595,7 @@ class Job(UnifiedJob, JobOptions, SurveyJobMixin, JobNotificationMixin, TaskMana
         new_prompts['_prevent_slicing'] = True
         new_prompts.setdefault('_eager_fields', {})
         new_prompts['_eager_fields']['job_slice_number'] = self.job_slice_number
+        new_prompts['_eager_fields']['job_slice_count'] = self.job_slice_count
         return super(Job, self).copy_unified_job(**new_prompts)
 
     @property
@@ -690,6 +691,9 @@ class Job(UnifiedJob, JobOptions, SurveyJobMixin, JobNotificationMixin, TaskMana
             count_hosts = 2
         else:
             count_hosts = Host.objects.filter(inventory__jobs__pk=self.pk).count()
+            if self.job_slice_count > 1:
+                # Integer division intentional
+                count_hosts = (count_hosts + self.job_slice_count - self.job_slice_number) / self.job_slice_count
         return min(count_hosts, 5 if self.forks == 0 else self.forks) + 1
 
     @property
diff --git a/awx/main/tests/functional/models/test_inventory.py b/awx/main/tests/functional/models/test_inventory.py
index e11a4f926c..97cf1cb0a0 100644
--- a/awx/main/tests/functional/models/test_inventory.py
+++ b/awx/main/tests/functional/models/test_inventory.py
@@ -46,6 +46,25 @@ class TestInventoryScript:
                 'all': {'hosts': ['host{}'.format(i)]}
             }
 
+    def test_slice_subset_with_groups(self, inventory):
+        hosts = []
+        for i in range(3):
+            host = inventory.hosts.create(name='host{}'.format(i))
+            hosts.append(host)
+        g1 = inventory.groups.create(name='contains_all_hosts')
+        for host in hosts:
+            g1.hosts.add(host)
+        g2 = inventory.groups.create(name='contains_two_hosts')
+        for host in hosts[:2]:
+            g2.hosts.add(host)
+        for i in range(3):
+            expected_data = {
+                'contains_all_hosts': {'hosts': ['host{}'.format(i)], 'children': [], 'vars': {}},
+            }
+            if i < 2:
+                expected_data['contains_two_hosts'] = {'hosts': ['host{}'.format(i)], 'children': [], 'vars': {}}
+            assert inventory.get_script_data(slice_number=i + 1, slice_count=3) == expected_data
+
 
 @pytest.mark.django_db
 class TestActiveCount:
diff --git a/awx/main/tests/functional/models/test_unified_job.py b/awx/main/tests/functional/models/test_unified_job.py
index f587e4c448..74e163c66e 100644
--- a/awx/main/tests/functional/models/test_unified_job.py
+++ b/awx/main/tests/functional/models/test_unified_job.py
@@ -152,3 +152,50 @@ def test_event_processing_not_finished():
 def test_event_model_undefined():
     wj = WorkflowJob.objects.create(name='foobar', status='finished')
     assert wj.event_processing_finished
+
+
+@pytest.mark.django_db
+class TestTaskImpact:
+    @pytest.fixture
+    def job_host_limit(self, job_template, inventory):
+        def r(hosts, forks):
+            for i in range(hosts):
+                inventory.hosts.create(name='foo' + str(i))
+            job = Job.objects.create(
+                name='fake-job',
+                launch_type='workflow',
+                job_template=job_template,
+                inventory=inventory,
+                forks=forks
+            )
+            return job
+        return r
+
+    def test_limit_task_impact(self, job_host_limit):
+        job = job_host_limit(5, 2)
+        assert job.task_impact == 2 + 1  # forks becomes constraint
+
+    def test_host_task_impact(self, job_host_limit):
+        job = job_host_limit(3, 5)
+        assert job.task_impact == 3 + 1  # hosts becomes constraint
+
+    def test_shard_task_impact(self, slice_job_factory):
+        # factory creates on host per slice
+        workflow_job = slice_job_factory(3, jt_kwargs={'forks': 50}, spawn=True)
+        # arrange the jobs by their number
+        jobs = [None for i in range(3)]
+        for node in workflow_job.workflow_nodes.all():
+            jobs[node.job.job_slice_number - 1] = node.job
+        # Even distribution - all jobs run on 1 host
+        assert [
+            len(jobs[0].inventory.get_script_data(slice_number=i + 1, slice_count=3)['all']['hosts'])
+            for i in range(3)
+        ] == [1, 1, 1]
+        assert [job.task_impact for job in jobs] == [2, 2, 2]  # plus one base task impact
+        # Uneven distribution - first job takes the extra host
+        jobs[0].inventory.hosts.create(name='remainder_foo')
+        assert [
+            len(jobs[0].inventory.get_script_data(slice_number=i + 1, slice_count=3)['all']['hosts'])
+            for i in range(3)
+        ] == [2, 1, 1]
+        assert [job.task_impact for job in jobs] == [3, 2, 2]