The problem is not the shoes or the weight. It's a muscle issue and walking form.
Read the book Born to Run. Walking heal to toe is the worst form you can have. Most folks tend to walk on their heal more than the mid-foot.
The next issue is muscle tightness in the calf and hamstring...both pull on the achilles causing heal pain. Combine all with hills and you get pain in the heals.

Focus on 'not' doing heal striking but 'not walking' on your toes. Stretch before, during, and after.
Wear decent shoes with decent padding but I've found ( after 4000k miles ) that all the inserts, expensive shoes, orthotics, do more damanage then good.
The other issue is that if you walk too far, too fast, too heavy, your going to have foot pain.

-smooth