In fact, by playing an assassin you are more likely to fail to realise that, if you don't got on what makes it likely to work.

If you do, it's easy.

I played probably half a dozen assassins before I cracked it. Then I realised it is op. Which is what I would have thought from logs.

I am not "missing" that. I completely understand your logic. I agree that in some cases it may apply. But often you do not need to play something to see that it is overpowered.

And let's note also that, putting me aside who played one of the first champions, that multiple recent champions have now said the build is out of balance.