LMFAO what?!?! This is the most ridiculous thing I've ever heard! First of all, ALL of swampert's base stats are higher than quagsire's. Furthermore, swampert has a much larger physical movepool than quagsire (he actually gets outrage and superpower, which quagsire doesn't). In terms of support moves, he also gets stealth rock, which quagsire doesn't. Granted, quagsire does have recover and better abilities, but he can't hit as hard and he can't absorb attacks as well as swampert can. So, he by no means outclasses swampert.
Too be fair, a pokemon's useage in the ladder is determined by it's ability to accomplish a specific role, base stats and whatnot are important but really, it's a combination of movepool, typing, stats,ability and the current metagame that determine a pokemon's usefulness and reason to use it.
Swampert was a great pokemon last generation but with fifth gen, it's definitely fallen and not really able to keep up with with Quagsire and also Gastrodon i suppose in the role of general bulky water. Quagsire has very decent bulk and with the addition of recover, stockpile heck even curse in combination with either water absorb, giving it an immunity and futher recovery or unaware, which lets it switch in on stat boosters makes it a much more potent defensive threat than Swampert. Heck, Quagsire even gets access to encore and yawn so it does have pseudo shuffling. Come to think about it, the only thing Swampert has over Quagsire is Stealth Rocks.
Swampert is by no means a bad pokemon but it is pretty much out classed this generation. If you're looking for a physical attacker then i think there are better options than Swampert. Outrage? How many Swamperts actually run it? Also, if anything, Quagsire can absorb attacks better than Swampert does because he actually can ABSORB water attacks and laughs in the face of stat boosters.
