A few remarks.
- The branch development model is just that, a conceptual and organisational methodology; it doesn't imply that said branches are big or small. Many people are simply asking for smaller but more frequent chunks of new content (many small branches rather than too few big ones). Which has nothing to do with them being broken —less content means less testing; bigger content updates means extensive testing due to higher risks of breaking the existing. It's a matter of choice. It's actually a general trend in the software industry to aim at smaller, more frequent updates (see: Operating Systems, Web browsers, creation suites, etc.) It's actually often considered easier to maintain quality, since you can address tuning, fixes and customers needs on a much more frequent basis, it makes a developer seem (and indeed be) more "involved".
- The WoW model of rolling out new content seems to be —unsurprisingly if the rest of the game is any indication— the one having been chosen for ARR (every 3-5 months, ~3 times a year). However, that game is old and, though it did set the norm a while ago, since then other development teams have addressed the matter of what is essentially perceived as too long wait times between updates. For instance, people have praised GW2 and STO for their frequent updates; a model that is not without bearing some resemblance with other engaging media such as series: new episodes every week, new features every months, major thresholds every quarter.
- Further considering the WoW model, even they did move from linear patches to more asymmetrical updates: (roughly) X.1 is a smaller update, X.2 a bigger one, X.3 a smaller one, and so on. They actually have 3 teams at work: one maintains the mainline, one works of the next patch, a third one on the patch after that (giving each team not 3 but 6 months to produce content, making updates more substantial). That seems to please players more than the old, linear way.
- The QA process of FF XIV is, curiously, quite different from the norm in MMORPG. Most use a public test server (PTS) so as to make sure that content is not only bug-free (as much as possible) but above all well-tuned prior to release. Many veteran MMO players will testify to the fact that there's pretty much no way to ensure tuning and debugging without the participation of thousands of beta testers, something which a company simply cannot perform internally.
- Therefore, somehow "crowd-sourcing" the testing on a PTS, using the 1% of the player base that constantly seeks for new content (usually a much hardcore subset) is a very valid way of raising QA and feedback to a whole new level. Even Blizzard, who's not the worst studio out there, regularly emphasised the invaluable contribution that PTS feedback brings to the fine-tuning of content. These live testers essentially "work" for the rest of the player base, for free (well, they actually pay for it…), and in the meantime they're happy because they get to experience new content on a much more regular basis (in exclusivity on a PTS, then for real on release).
Not having a PTS for such a large project was many times brought up by veteran gamers as odd, not to say worrying —and indeed, way too many bugs and mistakes in tuning show up on release servers, being fixed way too late after the content was rolled out. This will not change, no in-house QA team has the means to outperform live beta testing by thousands of players (who are keen on theory crafting the hell out of new content, as well as trying to push features to their limits). Meet the power of the crowd!
There is an argument against PTS: that it breaks the "surprise" of new content. This "spoiler argument" may seem relevant to traditionally secretive companies such as SE, but it doesn't hold much water compared to the benefits provided by PTS (see: Blizzard also being quite the secretive type with their future games and expansions), and frankly players don't care that much that new content is known before it comes. Typically, a few "surprising" features can be kept secret (not rolled on PTS, solely tested by the QA team); and new expansions, not patches, are the real deal when it comes to surprising players.
So, there you have it.
1. PTS should be used to speed up and improve QA, which is not bad but at the same time not particularly great in ARR.
2. Smaller content updates are a new trend much appreciated by players because they can "live with" their game, rather than "wait for" new content too often: it's much more engaging, and favours a much higher retention on a month-to-month basis, according to my sources —it's harder to make them come back if they're used to leaving between every patch, and WoW does suffer of that as subscribing numbers are on a general downward trend during each expansion cycle.
Just my 2 cts on the matter. I think my sig actually sums that up quite well, it actually goes true for players as well as developers.