Rek'Sai buffs/QoL changes
Passive: Increase the healing to be actually respectable. Something like 5% missing health plus current numbers might work, but IDK. Alternatively, allow her every couple minutes to utilize her old ult as her passive.
Q: Unburrowed: For every stack of fury, increase this abilitie's range and basic attack range by 1/7 of what it is now. Burrowed: Increase it's hitbox by a small amount.
W: Unburrowed: Maybe deal a small amount of damage in a very small area when burrowing. Burrowed: Reduce the lag between an enemy moving and the tremor telegraphing it. Allow tremor sense to see cloaked and invisible champions, because even if they're out of sight doesn't mean they don't interact with the physical world.
E: Unburrowed: Add a DoT poison after the bite that scales off AP. Not much damage, but not a negligible amount either. Burrowed: Increase the distance between created tunnels slightly. For the love of god, make it so that most forms of CC and displacements don't affect Rek'Sai while she is tunneling. Don't make her untargetable, just make it so that things like Yasuo's empowered q or Thresh's q will only damage her while things like Braum's ult will.
R: Same thing with tunneling; when I'm underground, after I ult but before I actually start my attack, I shouldn't be able to be decimated by Illaoi's tentacles.