And there really are a staggering amount of build variety in PoE at this point, much more than most RPGs and certainly way, waaaaaaaaaay the fuck more than in the IE games.
Are you kidding me?
You can still distribute your skill/attribute points randomly as everything influences everything to a degree, and play just fine with that character. The minuscule differences from an "optimized" build don't even matter on PotD, except for maybe a handful of fights, and that's hardly an argument.
The only "build option" is your choice of class, but from that point on, it's all the same. In the IE games you at least had to understand the system to create a good starting build. But from that point on, both the IE games and PoE offer very little in terms of advancement choices.
And in Pathfinder/D&D3.5 there were many ways to build very different but working characters within the same class. Because it has feats that are actual game-changers and not just a few % here and there.
Really, what will make one druid build notably different from another?
I do not agree your assessment on attributes, at least not for all classes. I would use Priests as an example. You will have different stat priorities depending on whether you want to be a buffbot, a damage dealer, or a melee Priest. More specifically, the difference between these three builds is how much you need Might/Intellect, Perception (spell or melee accuracy), Resolve (interrupt resistance), and Constiution. A heal bot typically just needs Might and Intellect. A glass canon definitely will want a mix of Might, Intellect, and Perception. Unlike the first two, a melee Priest will want Perception, Resolve, and Constitution. Priests have a lower endurance ratio and beginning accuracy, and so you need to compensate for this on melee builds. In my opinion, the class is too squishy not to optimize your stats if you want a melee build. In fact, I do not think you can have a valid melee Priest without some balance of Constiution, Resolve, and Perception on PotD. Alternatively, there is a melee Priest of Skaen build that focuses on sneak attacks, but I do not know enough about it to comment. For this reason, I disagree that stats can be randomly assigned for any class.
Another point I would make is that accuracy and concentration matter. In early game and even late game encounters on PotD, I would argue a little extra concentration or accuracy can go a long way (i.e., more Perception), especially with the difference between a glancing blow, a full blow, and a crit. My favorite example is the Twin Dragon fight in the White March. To give background, I had a glass canon Priest that pumped Might and Intellect (and some Perception) and that dumped Resolve. My strategy was to self buff my Priest (reached 40+ might) and dish out as many AoEs (Shining Beacon, Divine Storm, etc) as I could, and the rest of my party was a meat shield. The build was great, except when it wasn't. In that Twin Dragon fight, I essentially did no damage to the Dragons, because my Priest was either interrupted (little to no Resolve) or the Dragons defense threshold brought my spell damage down to practically nothing. At that point, my glass canon was relgated to a revive and heal bot (a shitty one at that), while the rest of my party took down the dragons (mainly my custom Wizard that focused on perception and conjured weapons).
My last point will be that the enemy AI in the White March focuses on casters from my experience. My cutsey glass canon build was fun, but often got screwed by ranged enemies or spell casters interrupting it. The Twin Dragon fight was not the only instance where I got burned for optimizing for just damage on my Priest.
The only counter example that comes to mind is fighters.
In the end, positioning and combat strategy will be way more important than the build.
On principle, I agree, but that is a slightly different argument than stats being irrelevant. If you create a melee Priest with little Constitution, Perception, or Resolve, then you will have a bad time.
One factor factor that I believe is missing from your analysis is that classes have different base accuracy, deflection, and endurance/health scores. This difference grows larger with each level. Based on the Pillars wiki (I cannot verify its accuracy), Barbarians have the highest endurance ratio, whereas Fighters have the highest base deflection and accuracy scores. In contrast, Priest has one of the lowest base deflection, accuracy, and endurance scores, and to rehash a point I made above, you need to compensate for these weaknesses in a melee Priest build.
