Totally disagree. There is not a single Pokemon in the game that is "invincible". That moveset has HUGE holes in it and can only be semi-effective against the in-game AI that is supposed to be stupid enough to let a 6-year old beat it.
You have already been given many examples as to how that moveset can be shredded. The best example is Gengar. Since it is Ghost/Poison-type, Toxic won't work on it. Since it has the Levitate ability, Mud Slap won't work on it. Since it Ghost/Poison-type, Hyper Beam won't work on it. Your only chance it the craptacular Double Team, but even after wasting 6 rounds using it, your opponent STILL has a 28.4% chance of its attack hitting. Again, a COMPLETE waste of time. Not to mention the fact a Pokemon with Aerial Ace or the crappier Swift are not affected by evasion or accuracy modifiers, therefore their attacks will hit 100% of the time. Plus, if you use Toxic on a Pokemon like Swellow, all you did was activate its Guts ability, which increases its Atk by 50%, ensuring that you will lose.
Evasion-increasing or accuracy-lowering attacks just aren't worth the time you have to put into them to make them effective. I couldn't even imagine how long it would take to defeat an entire game utilizing only that strategy.