Addressing Rek'Sai
I'll be very blunt cause I'm tired of hearing rek'sai might be nerfed again, I feel rek'sai might as well be reworked.
Her base skills are actually fine though, but her ulti when paired that's the issue.
It isn't a broken case like other things that need a rework but it's causing a bit too much disparity between skill and not in an interactive way as mechanics but decision making while also getting her continuously nerfed.
Her free vision/tunnels could be contested as an issue, but why? Her "free vision" fits her lore and pretty interactive in all cases it's used with proper counterplay, while her tunnels still provide roaming mobility at less of an extent but also an in combat dash which takes proper skill to make work.
Her ulti is just a stat-stick that just dramatically increases the tunnels' job and unlike tunnels it doesn't actually have counterplay in several of its cases.
Example someone sets up tunnels, you can go destroy them, lowering their roaming capability/mobility. While ulti, if they base they still return to a tunnel for free to immediately start farming; if they're counterjng topside jng and enemy is ganking bot, rek can still ulti bot for free, since tunnels would be somewhere the enemy would take risk to destroy over immediately ganking. Tunnels will be placed somewhere allowing her to have a global TP and one of the fastest at that.
There are many issues with rek'sai ulti and why it should be reworked.
I don't hate her current ulti, but E already sets up a better give and take(counterplay for effect) roaming tool out and in combat, even if one were to setup tunnels from base to jng they'd make a more interactive decision to give up map pressure and ability to traverse through jng, plus having tunnels destroyed would impact a bit more. In fact can't even think of a champ who already has a map roaming tool then free TP on top of it.
It's not interactive, every TP champ has a far more interactive ulti even TF who also likes the reveal and going in the enemy's face. Rek'sai doesn't use hers to flank but to just react to things you'd normally be punished for. Rek'sai uses hers to simply have less punishing setbacks. Head to base dw you have TP that you don't need for teamfights, go out of your path to CounterJng or get spotted dw you can tp to not lose map pressure, you gank a lane but the enemy is about to gank another TP and react in a reasonable time.
It's far too much of a skill depravity and not in a positive way, it takes knowledge to get value from not skill, which is fine in most other cases but not when it causes a skill depravity like this. It constantly gets her nerfed just because of the highest of knowledge players being rewarded too much.
Reworking it doesn't take away from rek'sai, which might sound dumb, but she'll keep her normal functions and map pressure via tunnels just not in an "I'm always there" type of way, still rewarding decision making without players going overboard. Overall properly keeping rek'sai herself without the massive inconsistency that isn't due to noticeable skill.
TL;DR- There isn't a need for ulti since E exist, and if it's retained instead of reworked reksai is going to just continue experiencing nerfs due to players who have knowledge of the game who use it just to deny setbacks.