Swampert is pretty underwhelming this generation as a utility Pokemon. He can hit a few things here and there with Earthquake and Scald and whatnot, but it's shut down by Rotom-W and the Grass-types that inhabit OU. Stealth Rock support is better left to stuff like Heatran or Tyranitar, and Gastrodon and the aforementioned Rotom-W can walk (or slither?) over what Swampert can, and more efficiently.
Back when I used Swampert in May or June this year, it was pretty decent, and I had a team which got to the top 2% of the OU ladder. Nowadays, most people don't even expect someone to get past the top 20% with Swampert on their side.