Before I begin talking about Samurai specifically, I'll start by saying that there will be a "tl;dr" at the end, since I know this will have to be across several posts.
Now, we've all undoubtedly experienced how changes to classes/jobs between expansions has left some people feeling alienated, and others feeling rejuvenated. This, I feel, is perhaps the most important aspect of discussion that we as a player-base should be having. For example, you will see what I'm referring to-- if you are not already acutely aware from your own experiences-- in discussions pertaining to 3.0's original implementation of Dragoon, 4.0's implementation of Monk (and subsequent 4.5's implementation of Monk), and so on and so forth. Some people will refer to this concept as the job's "identity," that which embodies the core values of what the job should focus on in its current incarnation and going forward.
There are, of course, jobs that have not changed significantly between each expansion, and one needs look no further than Black Mage to see the perfect idea of what a solid line of "identity" or "Battle Design" is. It is for that reason that Black Mage has merely evolved with the new additions to its kit and, simply put, stands less a chance at alienating the players that have played it since its inception than, say, those players that enjoyed 3.x Monk versus those that enjoyed 4.5's Tornado Kick-centric Monk (speaking of those who wish to play "optimally," or "to the job's fullest damage potential," obviously). One of the biggest reasons for the disparity in the reception is because there doesn't seem to be a true stated goal for some of these jobs. After all, if the Battle Design shifts unexpectedly or drastically from one expansion to another, it is almost certain to alienate players who enjoy the current incarnation of something versus its future incarnation. For example, we know that Dancer is a support oriented class, and it was stated as such during its reveal. At this point, we would expect a 6.0 Dancer to continue its current trend and provide stronger or more varied buffs and support effects in the additions to its kit. Having the knowledge of that Battle Design or "intended identity" lets you know what you're getting yourself into when you decide whether or not to invest time into the job.