Well, he did mention that future expansions wouldn't require it, but at least in the interview I saw (about which many players said just what you did), there was no suggestion of anything being a mistake here. The patches that were written to be a lead-in to Heavensward are required for Heavensward, naturally enough. They won't be required for the next expansion because they don't relate to the next expansion. Their story is about the current one.
Well, you are doing new stuff. Those quests are one-time only, so if you're not past them yet, they're new.
Except that we're not talking about filler quests. We're discussing the Main Scenario of the game. Sure there might be an occasional quest here and there where the story drags a bit, but overall it's a good story, and more significantly, it's the focal point of the whole game. Throughout FFXIV:ARR, you've seen how nearly every feature is unlocked either directly through the Main Scenario, or at least has a prerequisite that you need to have reached a certain point before you can unlock it. Heavensward is still part of FFXIV, so of course it follows the same pattern. The Main Scenario remains the focal point that determines what else you can unlock, just as it's been all along.
These quests form an essential part of the Heavensward storyline, so if you want Heavensward, they're a part of it. I can't believe the number of threads I've seen complaining about the fact that we were essentially all given the first chapter of Heavensward for free. The fact that you've paid for the remainder of the expansion is no reason to skip over its first chapter, nor to expect that you could.
Now, that seems like a more valid complaint. I wish they'd put the unlock quests (and level 30 to 50 quests) for the new jobs in the ARR areas, so that people wanting to do them could unlock and use the new jobs while going through the remainder of the ARR Main Scenario, before getting to Ishgard. It would, from what I understand, require somewhat different job stories, though, to match the location. I suppose that has to do with why they put them in Ishgard instead, and thus locked behind reaching it.





