Brendan, I am of the personal opinion that we shouldn't even show the actual regex strings in this page - much for the reasons you outlined above. Would you agree that only showing the actual regex string when you view/edit a selected Data Pattern? If not, what would you suggest?
The only other thing I can think of would be to truncate the regex string with a "..." at the end of the single line. Then the view would be uniform, and if you wanted to see more, you could either select the checkbox for the item you want to view and click the view icon up top (but that's the "old" way - which I don't like and would like to change, but that's another topic) or the "..." could be a link that would take you to the view page for the data pattern you clicked on.
I think not showing the Primary Pattern is probably the right choice. TMI for the list view. If people need to see that level of detail, they probably already know which pattern they want to view. No value in showing the full pattern in the list view.