Onto the meat and potatoes of the patch, unit balance! While it seems like there's a lot, overall the changes are fairly small. A few units got hit harder than others and a few buffed more than others but overall the general meta isn't getting drastically altered from this balancing. Alright let's tackle the one cost units...

Out of the gate is the two Woodland Druid combo getting nerfed slightly.
Maokai and
Ivern early game pair insanely well together and while these nerfs slightly hurt their two-star variation they are still viable to play. Interesting to note is they got their three-star variations nerfed so that hyper-roll Woodland isn't as good as it was. I had seen it still work on PBE but it'll be important to keep in mind they won't scale as well later into the game so only go that strategy if you really high roll your units. Still these two have a great early game and the balance changes don't change that fact.
Nasus and
Vayne got some slight shuffling in their stats. Bit better as a one-star unit, bit worse as a three-star unit. They are still the hallmark duo of Light hyper-roll but as with Woodland just keep in mind they won't scale quite as well later. Do note all these small tweaks to Light add up thus making the composition overall weaker.
Taliyah definitely needed a little love and she got it this patch. She feels much better to play now even with the small buffs.
Vladimir is a bit weaker and they seemed to mostly target his three-star stats but because Ocean/Mage is a popular composition he is still going to be a viable unit to pick up early game.

Moving onto two cost units,
Rek'sai and
Skarner got small changes.
Skarner definitely wasn't a bad unit before but he was out-shined by a lot of other units, these changes just make him a bit more appealing.
Rek'sai lost some power as a three-star and gained it in her one-star form but overall is unchanged. Mainly what this means is
Skarner is a more viable option as a front-liner in Predator compositions where you don't hyper-roll and
Rek'sai is still your go-to for hyper-roll Predator.
Thresh received great buffs which again adds to the overall power of Ocean/Mage. The incremental changes really add up and it's why the composition is becoming so dominant.
Malzahar is basically the same as before even with this nerf. While less health on his summons is good he still summons a lot of them so it doesn't make a huge difference. The Shadow nerf will have more of an impact than this nerf will.
Yasuo's scaling got slightly tweaked but honestly it's another non-factor of a change as
Yasuo 3 was fairly rare and you don't stay on
Yasuo 1 for very long.
Ezreal! He's actually somewhat viable now. He isn't a hyper-carry but with a Seraphs he can do work, especially when paired with a Luden's Echo.
Brand 1 got a decent buff which again just adds to the power of Ocean/Mage. While your goal is
Brand 2, the fact he can be fine to run as a one-star really boosts the power of Ocean/Mage if you find him early enough. Honestly he didn't need any balancing as he's already the best Mage in the game.
Olaf got slapped by the nerf bat a bit alongside the Glacial nerf. It's definitely noticeable as he takes a lot longer to get his ultimate off but he's still just as strong as before when it goes off. There will be less overall hyper-carry
Olaf's running around but if you position him correctly he is still a viable unit.
Yorick, another very strong unit in 9.22, also got nerfed but unlike
Olaf he was still played
a lot on PBE. I wouldn't be surprised if he received more nerfs in the future because his minions are still just so tanky and do a lot of damage. The main change for him is Light overall got a nerf so try to play him more in Summoner compositions or just as a strong front-liner.

Very small buffs to
Malphite and
Ashe. Warden got buffed too but
Malphite is basically the same as he was; an okay front-liner with decent CC.
Ashe, unfortunately, is still very underwhelming. Whether she needs more attack-speed, damage or a change to her kit I'm not sure but I've yet to see her be a true hyper-carry in 9.23 on PBE.

Alright let's talk
Singed.
Singed is a really good unit and honestly these nerfs don't really do much to stop him (because he's unstoppable ha ha) from being one of the best units in the game. Still tanks a lot of damage, still does good damage and Poison was completely unchanged.
Taric, on the other hand, is pretty underwhelming by comparison as a five cost unit. Not terrible for soaking damage and his ultimate can be good but the power difference of him and
Singed is crazy.
Taric and Crystal may need more buffs in future patches.