I'd imagine that if you were trying to amp up DD's sales have a two or three part crossover with New Avengers. He's already on that book so it makes sense and if he has this dangerous drive with all this information wouldn't it make sense to take it to his buddies in the Avengers? There'd definately be a bigger audience that way.
In terms of long-term historical performance, you'd be right. However, in terms of short term performance, AVENGING SPIDER-MAN is the better selling book. December's 2nd issue dropped from it's 100k debut, but it's still selling over 60,800 copies. NEW AVENGERS sells just shy of 53k and has struggled to sell over 60k beyond for bumps from crossovers or variant covers for a year or two now. There were times when it could sell over 80k without any aid, but those days are gone on the title. So I imagine editorial figured this based on the huge debut of AVENGING SPIDER-MAN more than anything.
In theory I do agree that it would make more sense for DD to trust his Avengers buddies with something like this; on the other hand, running to the Avengers for every problem can become an easy fix. Remember, DD and Spidey have been friends far longer than they were Avengers, and DD only became one recently. In practice, though, I'd rather be forced to buy a Zeb Wells or Greg Rucka book than a Bendis book. He's pretty much made Norman Osborn a Luke Cage enemy by this point.
This is a fair view. While I don't want constant crossovers a few like this aren't bad and actually lend importance to the story. The venom upcoming crossover and this are good examples of doing something right. (just a shame those books venom was going to push got cancelled)
Well...the VENOM crossover is basically challenging it's small but loyal audience whether they are willing to buy one issue of it a week for a month (which because this is a leap year, February actually has 5 Wednesdays). Especially issues handled by other creators starring characters, as you said, who have been canceled or are past their prime (Red Hulk). Historically this sort of thing tends to backfire. DC's proven to have gotten more out of gambles lately than Marvel - even if DEFENDERS and SCARLET SPIDER's debuts have done well.
At the very least, Marvel isn't challenging readers to buy issues of X-23, GHOST RIDER or HULK, probably because the latter two got axed.
That said, the smaller "events" tend to be better controlled and written. I actually liked SPIDER-ISLAND. While SHADOWLAND was flawed, I did find it more efficient than the usual line-wide event. And this is even smaller than that, really. It's only an issue from one book each, and two of them are still $2.99, at least.