I think that this is an interesting article on the effectiveness of Rugby Tackling vs. Football tackling. Maybe our Defense can watch some rugby video and get a few pointers.
http://www.wsj.com/articles/what-the-nfl-can-learn-from-rugby-1442335267
http://www.wsj.com/articles/what-the-nfl-can-learn-from-rugby-1442335267