Mhm, I see your point.
First, I just want to let you know that I have played with Sandslash before. It's not garbage (like D-Rank) but...once the novelty wears off, one can see Sandslash is quite the average shrew.
Second, Adamant Sandslash under the Sand hits a max of 458. Scarfed Lando and Thund-T hit 496. This is why Jolly is a preferred nature as it can hit a max of 502. So some of your 2HKOs might turn into 3HKOs or lower.... :/
Third, Scarfed Lando-T is pretty rare haha. But if you see one then hey. There's a kill for ya.
Fourth, hopefully I have got this across to you but Sandslash's inability to OHKO leaves it vunerable to taking massive damage. Not to mention LO Recoil. This means in practicality Sandslash's sweep might not last for so long.....
Fifth, Sandslash is pretty intimidating. However as the analysis says "It's also worth noting that Sandslash, while extremely fast in a sandstorm, can still be outpaced by a good portion of OU, namely Choice Scarf Latios and Starmie, and OHKOed by the appropriate move... In the end, checking Sandslash will boil down to exploiting its mediocre offensive stats. Don't be intimidated by Sandslash's Speed stat as, with the appropriate Pokemon, it can be swiftly brought down through calm and intelligent play."
Finally, I'd like to throw in a little argument for the sand genie. Landorus is more popular with Special LO and Choice Scarf...however his SD sets are still existent. His sets are even more deadlier as Landorus has Sand Force and Life Orb to pack a punch. Better yet, Landorus can use Gravity to smash through, would be Counters. Sadly the shrew lacks such luxury :/
Sandslash has potential....if it were given a bit of a boost. Easy to "gimp", relatively easy to wear down and stall out, short "life-span". All of these factors realllllyyy hurt Sandslash as a sweeper. He definitely is better in practice than on paper (I speak from experience). However, he still just doesn't have it in him to make himself a top-tier threat.
So rankings? I'll leave that up to the other people to decide :)