Comics market continues to grow. Its growing in a number of ways. Regular book market, digital sales, webcomics, subscription services like Marvel Unlimited or Scribd, and regular old comic shops. Its difficult to tell by how much because we only get numbers for the direct market (comic shops) and nothing from book stores (until at the end of the year I think), amazon, comixology, websites like Instocktrades or even purchases from libraries.
And yes, double/triple shipping titles is ultimately a bad idea. You need a really good editor per title to make it work and there arent gonna be enough to go around. Also, comic shops have to order books with some time before theyre actually released so the shops are forced to buy 3 issues in to a title before they can even gage reader interest. If a title is a dud. its the comic shop that suffers.
Marvel is much worse than DC in that regard. They create some very difficult benchmarks that shops have to hit in order for them to get specific variants. Ex: In order to qualify for a lot of the hip hop variants, shops had to order x2.5 of their previous order numbers of some title in order to be eligible to buy some of the variants.
Also, double and triple shipping tends to crunch deadlines and strain your talent. Simply put, artists are gonna get burned through no matter how many 'regular' rotating artists you have. Marvel and DC are kind of just squeezing the direct market for everything they can right now and shops are stuck in the middle.
Its pretty hard to tell what will happen next but a lot of people think Marvel and DC are in for a couple of rough seasons.