75 takes is crazy for a TV series. But I think the main issue with Scott on Blade Runner (and Alien) was not so much the amount of takes but rather the amount of time he took to set up each scene. The bulk of each night's shooting time was spent getting the lighting and props just right. And that is why it looks so incredible. Fast forward to Alien: Covenant and you now have a lot of very average shots mixed-in with Scott's otherwise awesome cinematography.
With regards to rehearsals, in the Prometheus documentary Rafe Spall says there were no rehearsals. Lots of stunt rehearsals though but that's not something you can ever skimp on.