Uhm it does you just need to aim it right, so probably since the opponent is a Bastion you need to get closer.
You intercept attacks in a straight line (that bar) and attacks that fall outside of that bar wouldn't get intercepted by defence matrix. So to closer you are against offensive ulti's the more it becomes useless.
http://overwatch.wikia.com/wiki/Defense_Matrix
Also did they buff Reinhardts charge? It feels that any secondary target he is hitting gets more damage right now