Coaching helps you get into the correct position -- making the most of whatever hamstring flexibility you have (and it doesn't take a whole lot for a deadlift) -- and hold it there. Lots of people are fine on the way up and get sore or tweak something on the way down.

A coach can also work you down into position from a higher start position if it is truly necessary. That approach doesn't take long if you know what you're doing.

Even without a coach, you can video what you're doing and at least answer the question of what's happening with your low back so you don't have to guess as you are above.