We probably wouldn't be having this discussion if we had team preview, but because we don't it becomes challenging to counter Togekiss since from my experience people wait until mid-late game to bring it out, when your counters are already weakened/fainted. With it's ability to set up Nasty Plot/Substitute fairly easily on defensive Pokémon, while also having access to Roost/Heal Bell/Aura Sphere, it makes it pretty difficult to deal with if your counters have taken prior damage. Combine all of this with the skill-less flinch spam, I wouldn't mind if it were banned, or as Mike suggested at least tested for a month or two.