Balance is always a major challenge in games. I know 20 year old 4x games which are still getting balanced by modding communities every now and then.

Riftborn expanding can be slowed down by playing with sparse resources. As a matter of fact, I generally recommend playing that way. The AI gets enough bonuses anyway on higher difficulties.

Unfallen are supposed to be a slow faction. In a hand of a player, this isn't much of  a problem. Though, that can't be said about the AI. Decisions matter more here and this shows.

For Cravers it's natural to just collapse at some point when they can't expand anymore and just have depleted systems left. 

Disclaimer, all games I play are huge galaxy, endless difficulty everything, 1 of each faction (including me as one of the factions)

I was actually just about to make a new thread saying how happy I am with the current balance. I don't know when it was changed/updated. But I just played through 3 or 4 games on the most recent patch.

Vodyani, I could never win with them before, but won quite easily on my last game, finished the quest too, but didn't really like the new bits at the end because of the academy faction.
I also had the first game I have ever had where the AI Vodyani was good. They were the 3rd or 4th most powerful faction in early and mid game. This was me as the unfallen, I forced peace on my 3 nearest neighbors, riftborn, vodyani, vaulters, and we had an easy win. Vodyani were beating up on me and the riftborn, but would of died to the vaulters before this.

Unfallen, again, a faction I could never do well with, but my first game with them on the new patch, maybe I just stumbled upon a good fleet setup. Light-class? (mid level coordinator) withfighter, bombers, and full tank. carried me through all of the danger as I vined3/4 of the galaxy and built my alliance.

Cravers, currently playing them in a game, I noticed the quest was much easier, seems like there is more depth in their gameplay now, but I don't like trying to juggle the population.

Obliterators, I didn't really have a problem with obliterators being OP before, but theAI never, ever, built juggernauts. In all of my games on this patch the enemy has favored juggernauts due to the nerfed obliterators, makes obliterators rarer, but maybe too much weaker. In myvodyani game the cravers launched 2 surprise obliterators, but I moved my arks and laughed at them. It is too easy to negate the damage with shields or moving once you see the trajectory of the missile, maybe overnerfed?
It also makes death stars (core cracker) worth while now, in addition to juggernauts, which I had previously only ever built for Hissho. IN my vodyani game I built 4 obliterators, I don't think the 2 missiles I fired reached their target before I won an economic victory. The whole time I was spamming death stars, I blew up around a third of the galaxy. Might be a bug relating to the AI targetting enemy death stars.

Nakalim, seem quite weak actually, for AI and Humans but of course I could be playing them wrong, the only faction tagged as "Powerful" when the AI plays them that do not seem to perform at that level... is there some small bug messing up the AI?

Umbral choir, still seem very weak for humans and OP for AI, but because of the nerf to obliterators they are less OP, behind cravers/riftborn/vaulters by a noticeable bit.

I was very happy to see some factions that had been cannon fodder in 90% of games actually doing well under the AI, like the Vodyani I mentioned. I also saw cravers, sophons, and Horatio get knocked out by other AI early, which had never happened before, unless it was cravers doing it.
AI Riftborn, vaulters, cravers, umbral choir, sophons, horatio still noticeably stronger than the others.

Hacking: I know AI Hacking was called too powerful when it first came out, or maybe in the beta? But I never thought so. Then it was nerfed. But now, was it changed again? The AI is really, really good at hacking. In my unfallen game, I had all but one defensive system on my home system. Cravers, my nearest neighbor, still managed to constantly hack it, picking the topple government option every single time. Beyond annoying. The enemy always stops/interrupts my hacks, but I don't seem to have any counterplay.

Off topic question. AI Umbral Choir, I detected their home system in my vodyani game, but did not have an option to invade (after I killed the ridiculous stack of fleets) is this a bug, or did they automatically warp away when I showed up?

Edit: AI Hissho and Unfallen are still criminally weak :(

Edit 2: Hacking, maybe it would help if there were more feedback when you, as the hacker, choose Topple Government or Rebellion (spawn pirates) give vision of the pirates and their invasion? Give a screen showing the results of the toppled government (did it cause anarchy in the capital? if just another system, are they mutinous?)

Off topic question. AI Umbral Choir, I detected their home system in my vodyani game, but did not have an option to invade (after I killed the ridiculous stack of fleets) is this a bug, or did they automatically warp away when I showed up?

Hard to tell what happened in your game. Usually, they transmigrate instantly when found. When they don't it's probably because they have moved not that long ago. 

Some games tend to be easier then others. Some can be incredibly hard. It often comes down to RNG and Galaxy Generation. 

In my last Vodyani game I had to travel a long way to finally find some Titanium. This didn't happen often before (even playing with sparse resources). It made the game much much harder.. 

It's hard to tell how the patches affect AI gameplay. Horatio got quite stronger a long time ago. Was always on the weak side before and now is often leading the points. Unfallen should be played by a human as they're slow growing trees and decisions matter more here.