"So research builds!" Yes, like I've been doing since Diablo 2. That's fine, but then why give a FFX-like skilltree? At that point you might as well lock classes into pre-set "trees" a la Diablo 2 and have people do the math and say "this is the best build for this function for this class for this patch. So far."
No. Fuck, no. I get your issue on some level which I will get to, but it's largely pedantism at this point. Sorry.
If you had played this for any considerable amount of time you'd know that you have a LOT more flexibility than you would in D2, as well as foresight into what works and doesn't, based on sane rules that are a LOT more intuitive and consistent than they were in D2.
If you made a sword build, you can se any skill that uses swords, simply swap the gems out. If you made a weapon agnostic one-handed or two-handed build, you can use any melee skill. If you specialized in fire spells, chances are you can swap in any fire spell, or respec for a handfull of points into another build because the elemental damage nodes tend to cluster. Or if you've only invested in general spell power, you can use any spell. If you made a bow user you can use damn near every bow skill, immediately.
You'll have to level the gems you changed, but if you've progressed to any degree into the game they can be leveled up very quickly because they don't suffer XP penalties based upon the zone level (they way your character does). So a level 1 gem gets 100% XP even if a level 70 zone. This doesn't obviate the issue entirely, but it makes leveling them up much much easier.
Changing paradigms completely is what's difficult, yes, but how is that different from D2, D3, and most other class based ARPGs, where it's actually impossible to do that with the same character? At least in PoE you CAN turn a bow user into a sword and board dodge tank, because every class uses the same tree.
You'll reach a point where you can draw an entire skill tree using the copy on their site to plan your build and know reasonably well how it's going to perform, too. The process is the same no matter what you choose to do. It's not like Diablo 2, where you fuck yourself with your stats AND skills incedibly easily unless you know 100% how the values work out and what you'll be up against, how to counter weaknesses with specific items and how to get those, etc. You also never completely screw yourself in PoE, unlike D2, when you mistakenly assume that a Skelly Necro needs to invest a single point into additional mana and waste a bunch of points better invested into life or dexterity. This counterintuitive shit just doesn't exist in PoE.
So you want to completely change how your character works at the drop of a hat. OK. THAT I get and that you can't do, but don't act like Skilldrasil needs it to make sense from a game design standpoint.
Lots of builds will utilized the full amount of respec points they have compiled to shift things around quite a bit once you hit that signature node.
The fuck are you talking about?
I have never once done that across the two dozen or so characters I've played. That's min-max shit for people who play a completely different build just to level. The only thing that comes close was when I re-specced my Spectral Throw Scion out of ranged damage nodes into additional sword damage nodes, because I noticed that I could get a couple percent more damage (and life) that way.