Most of the tanks are pretty weak right now, and despite his fat af heath bar, cho is more like a juggernaut despite Riot's classification of him being a mage.
Just to justify. Almost every tank has at least 3 CC spells 2 of which are hard CC (he has 1 hard 1 soft), they then lack spells purely for the sake of damage (cho spikes and R especially). Cho'gath's CC is then way less reliable (like dari, yorick ect) and fails to disrupt many people, lock down one person, catch someone out or peel effectively (the purpose of tank CC)
are pretty good at the moment, 2 of them for the wrong reasons. Amumu and sion deal too much damage, and secondarily scale in beef way faster than other tanks due to their kits and innate stats. Their damage is due to it being true/physical respectively meaning you can't completely nullify it with a single item like with magic dmg.
Because of this, they're winning through stat checks which certainly isn't healthy. A tank needs just enough damage that they can't be ignored and nothing more
Gragas also suffers this problem to a lesser extent, he just gets way too much free shit through stats alone. He builds full AP and is as fat as darius, builds full beef and can compete with darius for damage. (disclaimer, don't play dari, play mid/jg primarily just needed a comparison)
Rammus is situationally good depending on enemy team
But if we look at other tanks like
(desirable in pro play, weak af in regular play)
, all of them are health or armor based making them obscenely weak in a meta plagued with armor reduction and true damage. On top of that sej, shen and zac have been nerfed due to pro play, nautilus as well for 2.5 years non stop while malphite is situational atm.
Am curios as to your problem with ornn so if you could expand on that would love to respond :)