I've played a few more ornn games now, and now I can firmly say that his problem lies in the reliability of his cc, or rather the lack thereof. It's not even that his cc is too slow or too predictable, it's that it's so unreliable that he has to play absolutely perfectly to get it to work.
In my opinion that is fine, the better ornn players make him into a better tank, but that is also coupled with another problem. He utterly lacks usefulness if he falls behind. He can't build his tank items fast enough to compete with the enemies damage, and can't make good use of his passive because of how much he needs to back to not die to them.
If they made his fallback plan a bit more reliable then he would probably see a massive uptick in winrate.
And when I define fallback plan, I generally mean his q poke, and his w shield. If it were my decision, I would likely move some power around in his kit. Starting with changing his shield on w, as it is a pretty powerfu lability already, changing the shield duration to scale with level. This way as the game goes on he can make better use of his shield when behind but doesn't instantly become a monster when he maxes the thing. I suggest reducing the base value to 10% and having it increase by 1% every 3 levels. His a I would place more of the base damage and less on tank up, while having the ad ratio increase with rank. For example: 70 +30 per rank and 80% ad + 5% ad per rank.
This gives ornn more fallback power but doesn't allow him to run rampant early, or so I hope it does.