I've completed the South African Tiny 10 but find the original list more difficult as it typically requires travel and hunting to three different countries: RSA, Namibia (for Damara dik dik) and Mozambique or another country (for Suni, Sharpes grysbok and/or Oribi).
To date, I've got 7 out of the 10 and need the Damara dik dik (albiet, I did get a Kirk's Dik Dik in Tanzania), Sharpes grysbok and Suni.
Based on my experience and assuming one is willing to travel to the three countries, I would rank the Suni as being the most difficult to get, followed by Sharpes grysbok and then Blue duiker. The Suni is extremely wary and can duck into tight cover quite easily. By the time the PH determines if it's a male, often it disappears. Stalking it requires that the known small areas and trails where one has been seen are swept free of tree litter and branches so that a silent stalk can be made. Perhaps in other areas, they can be seen from the road and hop off to try to shoot, but where I was at in Mozambique, it was foot travel only.
Overall, the Steenbok and Gray (Common) duiker are the easiest to get so one could hold on to get larger or better trophies if they can.
The Blue duiker I hunted was with dogs and a shotgun pass shooting, so was quite exciting and intense in the East Cape of RSA. The pair was like a little blue blur running by heading for cover ahead of the dogs.
The Cape grysbok was hunted at night at the same location as the Blue Duiker. The concession was near the coast and close to Port Elizabeth, called Grass Ridge. I hunted with Induna Safaris near Kleinspoort in the Eastern Cape and was able to get the Blue duiker and Cape grysbok at Grass Ridge in the one day.
