I believe that gamefreak knew what they were doing when they made Swampert as powerful as it is. They just wanted to make sure that there would be at least 1 decent counter to it.
And yet, its best counter (Ludicolo) came during the same generation. I don't think Gamefreak has a certain pattern, I mean in Generation I all three starters were perfectly balanced; yet in DPP Charizard can beat both Venusaur and Blastoise with a simple SunnyBeam set. In Generation II, Typhlosion could beat Feraligatr with ThunderPunch (who couldn't OHKO with Surf) and Meganium with Flamethrower; yet in DPP Feraligatr has physical Waterfall to balance the trio. In Generation III the three were completely balanced, and still are. Generation IV was balanced by virtue of typing, but Infernape can beat Torterra with Fire Blast and Empoleon with Close Combat. Generation V could give us any number of these scenarios or a completely new one (like grass or water dominating for the first time).