Actually, Chris, you are misunderstanding me completely. I don't expect a streamlined build is the norm. What I am saying is that a streamlined build doesn't really offer a significant benefit over a build that just meanders along. The system is designed such that there is a very wide path that results in similar enough abilities (even if, on paper, the builds look different) that as far as mechanic wonks are concerned, they are effectively the same build.
That really is the key. An alchemist and spell caster look very different on paper. In practice, not so much. The same is true for an archer and a celestial wand/burst user (current system, not talking 2.0). They are mechanically similar enough to have minimal effect on scaling. But from the perspective of the average player, that doesn't really focus on the minutae of mechanics, these builds look very different (and unquestionably represent different role playing opportunities).
The real advantage, though, comes not by looking at how hard it is to optimize, but how difficult it is to make a bad build. It is very hard to make a terrible build by accident. It was a lot easier before fluid classing, but thankfully some genius introduced that idea.
For example, you can build a pyramid user instead of a column user. This is suboptimal. But it is only modestly suboptimal and not really bad. Furthermore, because of how the system works, it becomes LESS suboptimal as you gain levels and your pyramid gets a broader base. Similarly, as a fighting class, you could spend build on weapon master, style master, thrown weapon, and archery. This is suboptimal for pretty much every character. However, by early teens in level, the poorly spent build is mostly invisible (comparable to levels of weak racials or Craftsman skills most characters have. And because fluid classing exists, most suboptimal builds stop being suboptimal just by a change in class.
Truly bad builds are difficult to make and are almost always obviously bad. There is a big warning sign on artisan and production skills that basically says "not for combat." Just about the only trap that a person might reasonably fall into is trying to get an earth and celestial column before level 10.
And that is the important point. When you make it hard to create a really bad build that is a good thing. This is something that MMORPGs have literally done studies on (and since they have 100s of thousands of players, they have a darn good sample size). Building an awful build with your first character is one of the highest factors that correlates to players quitting the game. It is why most MMORPGs work tirelessly to make sure that no build can be awful. Alliance, whether by intent or lucky coincidence (I suspect a little of both, weighted towards the latter) has a system where building a truly bad character is hard and this is very good (tm) thing.
-MS