imo
Easy: Reyna/Sage
Difficult: Yoru
Yoru is easy to learn. His utility is very straightforward. The only reason it seems to be hard to master is to know what to use and when. Plus his kit is very expensive and very situational. I only see him viable on ascent, lotus, pearl and bind. And even then he cannot create space for the team unless he has his ult or flashes in and gets entry kills.
if u have a perfect combo with yoru and other utilities and players he can be broken but teams are not that good to use him that well so he is currently bad as if you played him in the same way you would in a ranked game he is terrible. The amount of things u can do with yoru like faking sites and the deception that he utility brings is amazing but teams dont know how to fully use this yet
i mean look at lcq and champs. Yoru has had the gihest pick rate their as its usually only prx who plays yoru but when EG and sentinels played yoru they did very well. EVen look at V1 they use yoru very often but nothing has changed since earlier this year so why only now has yoru become much popular? My conclusion is that teams are starting to understand how to utilise him well.
Easiest: Reyna, BY FAR(But also the most useless)
Hardest: Astra
Astra is very difficult, as your ability timings need to be very precise(Grav well and Pulse). But you CAN play her as just a normal controller. Pro Tip: Be a lurker, do your best nats impression, give your team all the util you have, lurk up somewhere else and go on a big flank. Astra doesnt need to be with her team, she has infinite range on her util, so dont feel enfoced to be another wagon on the one-way--train to the next rush onto a site.