The problem with betas is that they only really cover "does the game work?". They obviously do not cover "is this new expansion material balanced?" or "is this update decent?".
Every company worth their weight in salt does beta testing for patches and expansions nowadays.
I'm going to give SE the benefit of the doubt and say, it's possible they hit their quality ceiling before that started to be a universal expectation of customers. It's terribad customer service that they didn't comply anyway just for the sake of reputation, and one of the many things that has myself and others keeping a wary eye on SE. But, I'll go out on a limb here and say you shouldn't expect that to be the case this time around.
The profit model for MMOs requires staggering up-front costs, and relies on making back that money over time. 2010 is when nearly any company that could manage to scrape together the funds after seeing the success of WoW is releasing an MMO of every conceivable flavor. There's too much competition floating around for SE to go against the grain so obviously.
Even if the game had 5 years of beta, it wouldn't really do anything else than weed out more bugs than an 1 week beta.
Remains to be seen whether or not they can muster the receptiveness needed, but, Betas are for more than bug reporting. While you likely won't see a complete rewrite of game mechanics, you'll definitely see balancing, and responses to player suggestions. But they have to be the right kind of suggestions.
If there are 100 people in beta:
If 5 people want a cat-eared headband, this isn't likely to be listened to. It doesn't require much effort, but it only satisfies a handful of people and doesn't necessarily make sense.
If 75 people want a pet class, this also isn't likely to be listened to. It satisfies the majority of people, and it makes sense, but, it requires alot of effort and there was probably a reason they avoided it in the first place. They may have stayed away from it because Pet Classes are universally very difficult to balance in MMOs, and they might want to see their system in action to get a better idea of how to implement it fairly.
If 50 people want a dressing room, this should be listened to. It satisfies about half the people, it makes sense in a game that provides crafters the power to customize their creations, and it's a feature that's already been explored in other MMOs which means it's easier to figure out how to implement it.
If SE is avoiding the 1's, explaining to us why they won't implement the 2's, and gets cracking on the 3's in a timely manner they're doing stellar. Even if they can't be assed to explain the 2's, they're still showing a marked improvement over FFXI. If they ignore everything without so much as a peep, you're right, they haven't learned one **** thing.