Why put the work in on your backswing when impact determines the quality of your ball-striking?
Well, good swings keep the club on-plane throughout and a consistent backswing plane gives you the best chance of achieving a good downswing. The easiest way to do this is by starting the swing correctly with the required set-up and take-way.
If your takeaway is immediately off-plane, it will be very difficult to consistently return it to impact. Jim Furyk, as you might already be aware, is the exception that proves the rule.
Check your position
When the club reaches hip height, the hands, shaft and the clubhead should all form a straight line parallel to the target line. Upper right arm starts to fold whilst maintaining its connection to the right side. The hands stay in and maintain the same height as at address.
Something to think about
If the takeaway is outside the line, the swing is immediately off-plane and disconnected. Too far inside will likely make you lift, causing the swing to be too steep and over the top.
Practice the correct takeaway in front of a mirror by keeping your head down, then checking your position. Alternate from practising at normal speed to performing the move as slowly as possible.