what did the backing plates look like?
when you had the shoes off were there worn spots where the shoes ride? there should be raised spots where the shoes ride, sometimes they get grooves worn where the shoes move back and forth and this can cause restriction in shoe movement making the brakes act just like this. NO amount of adjustment will override hanging up shoes. Those brakeshoes must have full free movement against the backing plates or you get exactly this. If you find these grooves worn into the standoff pad area where the shoes ride you will need to install new backing plates as well.

just a thought to ponder while scratching your head ;o)