I think that Togekiss ban is not necessary but if you want a better META and better experience of the game maybe you should try a test ban or at least (NERF FLINCH RATE).
The Togekiss set: (Sub / Nastyplot / Aurasphere / Air Slash) is almost "Unstoppable". As the only the mains counters for this (Tyranitar / Magnezone) Become useless because you need to break the sub first and then kill the togekiss.
Ask @gbwead i was the 1st player to complain about this pokemon and now i always run teams with at least 1 togekiss counter. You should try a Milotic Timid (full Speed with HAZE) . The META is like that we just need to adapt.
252 SpA Milotic Ice Beam vs. 0 HP / 0 SpD Togekiss: 82-98 (51.2 - 61.2%) -- 94.9% chance to 2HKO after Leftovers recovery.
252 SpA Togekiss Air Slash vs. 0 HP / 0 SpD Milotic: 51-61 (30 - 35.8%) -- guaranteed 4HKO after Leftovers recovery.