I have had a good think about this one and I think I am leaning towards banning it.
The lack of certain Pokémon and legendaries doesn't favor this case right now. Without the likes of Zapdos and Rotom-W around, which would stop it in its tracks, this Pokémon really does end up being a problem to a lot of teams. I think there are definitely checks to Togekiss, because if there weren't any it's usage would be through the roof and it does have 4mss. However Togekiss doesn't just bring damage, it also has the ability to bring a little bit of support to a team with Heal Bell if it opts to run it.
As people have said above the sheer lack of skill this mon takes to just win games is simply so stupid. The ability for this Pokémon to just allow an opponent to not make a move for easily 10+ turns in a row is just a no for me. It takes away all the fun and skill from the battle. There is an argument to be made that you should just run Pokémon that are faster than it if you don't want to get flinched. Or bring Pokémon that can check it. But you don't just fight against Togekiss and by the time Togekiss get's revealed there usually has been a lot of chip damage done and/or Pokémon already fainted.
While this Pokémon can end up sweeping teams by itself, I think an even more annoying thing it can do is just tear apart any team with "skill" for any sweeper to end it right after.
Right now even with Togekiss in it I think OU is in a very very good place. I'm a little sceptical about what will happen to the tier if it does end up getting the boot. It doesn't single handedly define the entire metagame but it is a pretty dominant Pokémon in the tier right now so I am uncertain. But I doubt it will turn to shit.
And to be completely honest if TC is worried or unsure why not just testban it for a month or two?