I feel the nerfs will be very noticeable, especially to Rek'Sai players. I have noticed a consistent ability to get off at least three autos and a bite after a knock-up, which means at level 5 q, your combo will be doing at least 60 less base damage, plus the slight AD ratio nerf on the knock-up.
But she does have counter-play. Her gap-closer is incredibly unreliable since it always goes a set distance: you can't tunnel any shorter if you want to--the way Vi can just stop once she hits her target, or the way you can jump whatever distance you like from the min to max with Tryndamere--which means you will constantly be over-closing the distance, which often results in the enemy just running the oposite direction and makes trying to land the knock-up annoying and difficult. It can also be difficult to see them with the tunnel-vision mechanic and requires a whole new skillset to utilize properly.
She also has a cooldown on her ability to knock up any single target, so even though she can burrow every 3 seconds or so, she can't knock you up again for 10 seconds, and that time CANNOT BE DECREASED WITH CDR like other CC abilities can. Also, the amount of knock-up is dependent on how close to the center of Rek's tiny circle of effect they are, so if you just barely clip them with the edge, they are only knocked up very little. Compare that to Cho'Gath's huge knock-up radius and how barely getting clipped still knocks you up just as high as getting hit in the center.
And she may have truedamage with her bite, but without AD it's a very insignificant amount of damage in the grand scheme of things. And if you build pure AD Rek'Sai, you are an assassin and don't take hits well at all, which severely inhibits your ability to teamfight (as in you basically just run in and die before you can even get any damage out).
I personally believe what would be a more significant and useful change is to have her fury grow more slowly than it currently does. This would make her lane dominance less annoying because she wouldn't be able to regen as quickly, and would make achieving her truedamage bite more difficult/time consuming.
