Can you share your workflow, it's hard to tell when we can't see how you build the workflow.
Is the workflow canceled or finished?
The maximum count activity shouldn't matter in this case unless you have a loop going through the same actions over and over again or if you have a very large workflow.
You could use a wait for condition and make a script checking all tasks are closed before it goes on to the next stage.
This is an example we use (should probably use GlideAggregate instead of getRowCount for optimal performance).
//Set the variable 'answer' to true or false to indicate if the condition has been met or not.
var gr = new GlideRecord('sc_task');
gr.addQuery('request_item', current.getUniqueValue());
gr.addActiveQuery();
gr.query();
var count = gr.getRowCount();
if(count > 0)
answer = false;
else
answer = true;
