I'm a Solo Self Found player. I've made it up through T9 maps in the end game strictly under my own steam, and the wiki, at Level 88. I'd occasionally read someone's build and cherry pick a couple cute gem combinations (like Tempest Shield + Blind), but other than that I've never tried to replicate someone else's build, nor do I think that sounds remotely fun in a game as expansive as PoE. All my character builds are made by me, with some informed reading on some threads on the PoE forums but no point for point copying of gear or skill tree choices. A lot of my builds work because I've found decent enough uniques and Lvl 70+ yellow gear to support them, but that's pretty much every build in PoE. The only thing I've ever traded to get in PoE was a Shield Charge gem back before you could just buy gems from quest NPCs. I sell the occasional duplicate unique for a couple of Chaos now and then, otherwise I do no trading.
So yeah, I'd say it's totally viable if you have the time to put in to it, and are willing to table or shelve a character until the right gear is available to them.
RE: Fall of Oriath. What a mess for standard players. The entire expansion was already beaten when I logged in. They took away a large chunk of my skill points and locked them behind dumb side quests. So upon logging in and spending 30 mins remapping skill points, I just had to go each one of the acts, collect my rewards for the main quests and run some low level crap to get my missing points back, so I could end the expansion exactly where I started. What fun, what thrills.
So I have no idea what happened in the story. I ran down a couple of the story bosses just to see them, smooshed them and kinda went "meh." Talked to some of the story characters before I found myself scrolling through their dialog without paying any real attention. Mostly I was just jumping from act to act with no real sense of why, and little ability to care.
So thanks GGG. Always appreciate the standard love. I know their attitude is "Just make a league character bruh and replay the game for the 40th time!" but I can't be fucking assed. Also, the entire story seems pretentious as fuck. Even more so than the rest of PoE. I get who Sin and Innocence are, I just don't get why they take up so much of the story and their dialog with each other is particularly abominable. At least with the other characters in the story there was a direct connection between why they're opening their mouths and the game you're playing. Sin is literally just there to be a writer's mouthpiece (because of course "you can't harvest the power of the gods yourself so let me create a NPC tag along who does it for you") and it's not even a particularly good one. Also, why does it feel like every other normal human NPC in PoE is a sailor, a ship's captain or a smuggler? We got those two new smuggler characters that show up in all acts with, I swear, some of the cringiest voice acting PoE has ever offered. The chick in particular makes me feel like I need to take a bath after listening to her talk.
The gods too, who are supposed to be ya know, bad ass gods? Barely get any treatment other than "Hey go kill this guy." One of them doesn't even have a quest per se that I could find. I noticed there was a zone I hadn't explored after clearing the FoO and found the boss there, that I retroactively got a reward for after defeating. Their models aren't that amazing and some are even recycled assets, nor are their fights that cool. The areas don't feel like they're under their sway at all, they're gods in name only. Oh and one of the new Pantheon bosses straight up DCs you from the server at the same point in his fight, every time.
I've tolerated PoE's writing and story up until now but even I don't have the patience for FoO's self-indulgent tripe. The whole thing has MAGNUM OPUS stamped across it in 40 foot high letters, only it isn't that good.
All in all, I'm underwhelmed by FoO. Other than the new tilesets and a couple of new enemies, it mostly feels like recycled trash regurgitated into another 5 acts. I wasn't expecting the moon, but about the freshest thing in the expansion to me is the enemies who now launch an attack when they die by default, or the changes to Volatile Blooded enemies. The Pantheon System seems like a joke, yet another extension to the mapping system with a non-scaling pay off that most end game players will have wrapped up in a month.
I like the continuity now of kill Malachai --> watch Oriath Burn --> kill the gods --> become the Ascendant Emperor. That's a nice personal story arc for your character. But that's about the only fluff I find interesting in the whole mess.
Also this league seems like one of the laziest. An entire league to farm for shards of existing currency, or shards for new some currency that, other than the Mirror of Kalandara or w/e, seems mostly like junk.
If there is one silver lining to me in FoO, it's that the difficulty curve in PoE is now finally feels reasonable. I had exactly zero troubles with any of the major fights (I didn't fight Kitava so, maybe she's as ridiculous as pre-FoO Malachi was.) Granted my main is pretty OP for story content but still. I was expecting some GGG style difficulty spikes and didn't find them. Which I'm happy about. I feel like the real ball breaking content should be in the end game anyways, not in the lead up to the end game.