Some heel shots are caused because at set up you are too close to the ball causing your arms to start inside your shoulders
Casting, heaving and throwing your club on the downswing result in a tremendous loss of power because you release the club too early and exert the energy of the swing in the wrong location
Many slicers set up with their right shoulder too high, prior to bending over to get in to your stance try tilting your right shoulder slightly down then take your stance, this will allow your body to work more around your right side and eliminate that steep downswing