You often can't beat a good bar chart for getting a message across quickly and easily; perhaps with some highlighting for the key message (if there is one). Some ideas below.
I used this data:
And set up a pretty basic bar chart like this:
The [Max time] calc for the highlighting is: AVG([Time]) = WINDOW_MAX(AVG([Time]))
Aka: is the average time for this bar = to the maximum average time we have over all of the bars; if so highlight it.
Alternatively you might want to show the distribution of times (i.e. show each instance of the form) as well as the average or a median. You could do this in a number of ways, here is one where I've used a box and whisker plot (from the analysis tab):
Not the greatest example as I only created 3 form instances, but hopefully gives you the sense of this option. I switched to a circle mark type and dragged my ID onto detail so that I get a mark for each form instance. Then dragged box plot on from the analysis tab.
Let us know how you get on and whether you'd like some more pointers or ideas!