I'm not completely sure about hunters, the article is a 9 month series on equitation and jumpers. Although, in hunters, it is much more about the horse then the rider, I think having a slight outward angle of your foot to the horse would not be counted against you as long as it wasn't obscenely pointed outwards haha. The judges are looking at your horse and the way he/she moves and reacts to your aids, I don't think your foot angle would really play a huge part in the judging. In regards to dressage, I would have absolutely no clue, I know barely anything about dressage showing! Haha.
I know it's a common concept that the foot should be perfectly parallel to the horses body, but I think that is extremely uncomfortable, and honestly, gives me less usage of my legs as an aid. If the stirrup is as a slight angle to the foot, like George Morris says, your foot will only point out ever-so-slightly, and is actually in a much more natural position that wouldn't put nearly as much torque and twist on the knee aka much more comfortable! Lol.
Personally, I think the way he described it works perfectly, both with the way it looks and feels and I don't think you have a huge problem on your hands. Just check your stirrup length and be careful not to fully rotate your foot outwards so you aren't using the back of your calf muscle. If you have problems with your foot rotating more, use a haystring to tie your stirrups to the girth (although not too tight, it's way too painful!!) and practice like that. Having heels that go down too far is definitely not something to worry about either =P just relax and enjoy your riding!!