You arent taking in count that Dar Passage transport the ally towards you, and to use effectibly Thresh could need to be away of the teamfight for it to be effective, making the rest of his kit become useless in the meantime. DP could be more effectibly used in escapes when an ally is traped and flash is on CD, Thresh can pull them to him. OR to bait, or better position tanks lika Amumu or Galio. Plus, I think that your allies cant right click itthe lamp if they are stunned/rooted/suppresed, so it still DOESNT counter Blitzcrank, since the grab stuns AND is follow by a knock-up, not counting other ccs from enemy team. Its less OP that many think.