gliscor with a little sp.def investement(with only 20 sp.def evs and of course max hp,which all gliscors are running,gliscor survives swampert's ice beam 100% of the time)can survive one ice beam and 3hko swampert with acrobat(assuming swampert switches in on gliscor since you said switch-in) or fling him a toxic orb(or just use toxic) and stall him out with sub and protect...
and how is swampert dealing decently with sand?terakion,landorus,garchomp and excadrill all ohko after an sd...the only reason i can see to use swampert is being stuck in 4th gen standarts...the only useful set that swampert can run now is a choice band set but there are pokes like garchomp that have the same(if not better)bulk,better attack,better speed,better stabs so....
Yeah...Sand teams aren't always at +2, they generally will only try this when they have successfully weakened the opposing team (which means ANY checks would be useless.
Meanwhile, Swampert is as good of a check to Tyranitar as ever (especially since they all run Fire Blast and Ice Beam these days), setting up Stealth Rock and Roaring Ferrothorn when it tries to switch in. Surviving an Ice Beam isn't really that big of a deal IMO - Gliscor is relied on to check so many things it is rarely at full health, and even if it can survive, few people will be willing to let their Gliscor reach such low health just to defeat average offensive presence that Swampert is.
Garchomp needs an SD to defeat Swampert, otherwise the mudfish makes a decent switch into any other form. Leftovers SubChomp can't OHKO with Earthquake while Swampert will win by breaking the Sub and then KOing with Ice Beam. ScarfChomp gets walled and Pert can Roar the switchin to rack up SR damage.
SD Terrakion breaks Swampert (it also breaks Gliscor, btw), but Swampert comfortably deals with RP Terrakion, KOing it with Earthquake following a round of LO recoil and Stealth Rock. Balloon Terrakion also fails to 2HKO with consecutive 2 consecutive CCs while the SpD drop means that STAB Hydro Pump can OHKO even in Sand after LO and rocks.
Swampert still makes a great switch-in to Heatran (who is surprisingly high), SpD Jirachi, is a viable Water-type for use on Sun teams thanks to secondary STAB (and they will appreciate a Tar switch-in), and can deal with lesser threats such as Hippowdon, Tentacruel, and Metagross.
And despite tank Pert's usefulness having decreased, CBPert is still quite effective. Other users of the item have their advantages, but do not lure Ferrothorn as effectively as Swampert does. Other users of CB also tend to invest into attack and speed, as your aforementioned Garchomp, but Swampert will invest in bulk more often than not which distinguishes it. Finally, Hammer Arm means that Skarmory will eventually lose to it as well, which only a few other CBers can really claim.
Yeah Quagsire and Gastrodon have recovery and their other advantages, but Quagsire is pretty much useless until you face a threat at +2, otherwise it is taking unboosted hits worse than Swampert is. Same for Gastrodon - it had Recover last gen too, so all it really does is take Water attacks now (which is admittedly useful against rain).