I don't really call it high end of the ladder until 1900 when you might actually play someone who has a decent knowledge of the game, and knows the ability ran on every jynx that has seen the light of OU. At least one of those games contained hax that helped you immensely, and though you may have been on the upper middle part of the ladder, at least three of you opponents were in the 1600's and one was using Aggron (lol).
Enough has been said about Jynx. And basically, you're argument was it can sweep once its counters have been removed...only problem with that is the fact that its true for every Pokemon in existence.
Now, Thundurus-T, this guy is simply fantastic. He resists both of the most prominent priority moves in the meta, he has many viable sets, and few counters which can easily be removed with a small moveset change, depending on which counters your team is better at removing. Let's start with what is, imo, his least threatening set, but is still an extremely dangerous set. Scarf Thundurus-T can make a fantastic revenge killer with Volt Switch and fantastic BoltBeam coverage, and Focus Blast for Steels. With an already massive Special Attack stat, the scarf really helps him outspeed things that might try to revenge kill him. Next set, Expert Belt. This set is fantastic because when the opponent sees you not take Life Orb damage or use a set-up move, they'll more than likely assume the Scarf set (unless its a solid player). This set allows you to bluff scarf, and can also open up a move slot that would normally contain a set-up move. This slot can be filled with Volt Switch for fantastic momentum boost or Grass Knot, which can remove counters such as Gastrodon and Hippowdon. But to me the best sets by far, are its Agility set and Double Dance set, since their sweeping potential is matched only by the S Rank Landorus imo, since most Keldeo need a scarf to sweep and Terrakion suffers from weakness to common priority. His sweeping sets offer fantastic coverage, and the bulky EV spread makes him be able to take some hits quite nicely. he also doesn't even have to have a boost wreak havoc, he can go boostless and still rip holes. Now onto his biggest flaw, Stealth Rock weakness...which is covered by Forretress and Starmie who can provide a counter and check, respectively, to Mamoswine as well as spin, as well as perform well in rain just like Thundurus-T. The sheer versatility of Thundurus-T and his almost unmatched late game sweeping potential and raw power, as well as the fact his surefire counters are limited to Bulky Latias and Amoonguss, both of who are shaky against the NP set, and checks limited to Mamoswine (who is quite easy to get rid of since many of his counters are popular Thundurus-T partners) and other priority users once he is weakened. So, in short, Thundurus-T for A Rank.