Mence is Uber argument: If Swampert is in against Mence who's +1DD, then I'm assuming you came in after one of your Pokemon was already killed. In this case, Mence has already killed one of your Pokemon (not good). After you switch in, the Mence would just switch out, would it not? Therefore, your statement is invalid because if Mence sees a Pert, it wouldn't try to Outrage, but instead would switch out, eventually coming in later in the game to wreck more stuff.You have no reason to say that i don't know what i'm talking about, seeing as you have absolutely no idea who i am >_>
Swampert can surive +1 Outrage, and hit with ice beam for the KO.
Mence is OU argument: If you predict correctly and switch into a Dragon Dance, then good job and good prediction. After that, you can live an Outrage and OHKO with Ice Beam. If the Mence were to decide to switch out, then it's already taken LO and SR damage, only to switch in again sometime later in the game to take even more SR damage, after which point priority moves will make it easy to take down (Scizor). Therefore, your statement is valid, because Swampert can OHKO Mence when it's in the right situation, and is an efficient counter.