"Very little" seems completely impossible to argue. More effort than any other edition and than most RPGs, was the reality:
http://www.wizards.com/dnd/Article.aspx?x=dnd/updatesarchive
Remember this page? No other TT RPG or edition of D&D has been remotely as thorough, that I'm aware of (would have been even better with a free-to-access SRD though, if 4E had had that). We got constant updates, which happened BEFORE THEY APPEARED IN THE DDI (!!!!!!!!!!) too, and got discussion from the creators about why they happened which didn't require DDI access.
I was unaware of that, but I don't find it much different to Dragon-only classes, and considerably better than classes only in small-production-run books. Plus, I don't get what prevented you guys from sharing the DDI access.
In response, I'd say that my personal experience was that I greatly preferred it when there was (seemingly) less need for extensive errata due to proof reading and play testing, and that when it was truly necessary, companies made it available in print. Game companies did this one of 3 ways: reprinting the books containing the erratad material; printing standalone errata (most similar in nature to the web page you cited); presenting the errata in a an appendix in a subsequent book.
Don't get me wrong- the website does have its advantages- but if you want a hard copy of the errata, it shifts the printing cost to the consumer...who will not have the same economies of scale as the game company.
As for Dragon material vs DDI, there IS a difference. Most gamers I know didn't use Dragon material at all- in the 30 years I was a subscriber, I was the only one in my circle of gamers (covering several groups in 5 cities in 3 states) who ever did. It was the definition of "surplus", easily ignored. Dismissed as optional, because, while "officially approved" it all was optional. The odds that a gamer you knew was using something out of Dragon were small.
In contrast, DDI blended everything together seamlessly. Since all options appeared on the tables when brought up, you might not notice that something used appeared in Dragon. With the design philosophy of "everything is core", that's great...as long as everyone has access to everything. And everything remains hosted online. In a supported format.
If & when 4Ed stuff disappears from the DDI servers, the only folks who will have access to the Starpact Hexblade (and similarly limited release options) will be those who downloaded it.
Meanwhile, those like me who never wanted to pay the monthly fee, but bought the physical books instead? We never got to see those rules. We never got those options. And like the Deep Purple album I mentioned, it seems like gouging to ask those loyal customers to buy stuff twice.