Is there a way to know what killed you?

They are not intending on adding it from what I've seen. One thing I found useful was recording and playing back freeze frame to figure it out, as above post suggests. Have stopped doing this because always recording uses PC resources, but it was useful for learning. Now I usually have a pretty good idea based on what happened and my character weaknesses. I think it would be very useful for new players, but I think GGG believe it will cause more confusion.