You do know right that publishers never release sales numbers? I doubt any numbers on AssCreed 2 on PC were that great given how much of a disaster it's always-online DRM was with customers and in the media. Ubisoft are a corporation, they wouldn't do anything if it didn't have a financial incentive behind it, believing they renounced always-online DRM simply out of concern for customers after previously calling it a success doesn't make sense, no business is that schizophrenic. They obviously did it because the bad rep of always-online DRM was killing their PC sales numbers, otherwise why would they do it at all?
F4LL0UT: Publishers do feel some responsibility for their paying customers
They don't. They exist for profit. Publishers have no connection with anyone who buys their product versus anyone who pirates it, or anyone who complains about it on the internet, all of them are potential customers and there's no real distinction to be made, there just "customers".
How the freck would Ubisoft or any publisher even know who is a "paying customer" and who isn't?
If you think publishers think "paying customers" are in their cool super club I think you're quite naive, they couldn't care less who buys their stuff and who doesn't, as long as someone does.
The people who do "boycotts" on the internet like that lack sincerity. And who says a "boycott" is some kind of official declaration by an individual that they won't buy games from said publisher because XYZ reasons? It can just be any anonymous individual who decides they will not buy games with DRM, or for whatever reason.
Of course, on a micro scale what proves you wrong is for example Kickstarter. On KS it has become the norm that if you want funding to make a game, the developer will need to offer their official word that the game will be DRM-free, or at the least will have a DRM-free version. It didn't start out that way of course, it only became the norm after backers on pretty much every major project DEMANDED a DRM-free version, and the developer needing their money to make the game of course had no choice but to acquiesce.
The same logic can be applied to publishers, the money from gamers is what these publishers survive on, if no one purchased their games they would not exist. With that in mind, the concept that gamers can't exert pressure on publishers to end DRM practices is just wrong, it could easily happen. Most gamers are pretty inert and don't care too much/are fine with Steam, but the idea that it's impossible and DRM is ~eternal~ is absurd.