To hit the ball solidly with any kind of consistency, you have to have the clubhead coming down to the ball at the correct angle.
The bottom point of your swing and where you hit the ball on the face are dictated mostly by this angle of approach into impact. And angle of approach is dictated mostly by two things: the plane of your swing and the forward tilt of your body.
If you change the amount of bend in your hips during the swing—something I see all the time in tweets that include video or a sequence of pictures—you're also going to have to change your swing plane to match. And that's hard to do consistently.
Ideally, whatever bend you have from your hips at the start of the swing should be the same posture you have at the top (above) and through impact.
It feels great to hit a pure 7- or 8-iron on the range from a perfect lie, but playing golf is about hitting shots under less-than-perfect conditions. Try a practice session where you experiment to see how low you can hit a certain club, or how much you can curve it. Then you'll have some good experience when you need to get out of trouble during a round.
*Hank Haney is based at the Hank Haney Golf Ranch in Lewisville, Texas. To get fixed in Golf Digest, send Hank your swing on Twitter: @HankDHaney