I think you missed something in the definition of sequential art. The "convey information and/or to produce an aesthetic response in the viewer" part. A series of panels with a ball rolling does not fit that definition, unless the ball is doing something interesting, or if it is instructions on how to roll a ball.
The term Graphic Novel may be pretentious, but you are tilting at a strawman here. That term is not in widespread use here, as most of us call them Comics.
And for what most of the people in this forum, or involved with webcomics period want, yes, story does matter. For most people, it's all that matters. They don't care about the prose or the art, they want story, in an entertaining format. While there are some art-centric comics that have done well, most of the best received comics on the web are about story, not art, and not writing.
This is opposed to mainstream comics, where the writer is what most people are picking up a comic for.
As for reading a novel over a comic? I read comics due to the fact that when the medium is done right, it is a better story than a novel, a movie, or a TV show. Yes, story does matter, and the marriage of verbiage and visual is what makes comics work.
I don't even know where to start here. Let's try the OED, since we don't even agree on terms. Story: An account of imaginary or real people and events told for entertainment.
No mention of writing. Most comics are drawn from a script. Let's take the word Writer out of here, and replace it with Scripter. That script could be verbal, it could be a storyboard, it could be just a set of thumbnails, but in most comics, it is a written document.
Without that script, whatever form it is in, you have no story. Without the visuals, you have no comic. And no, words are never subservient to effective story telling, they are part of it. All attempts at silent comics (that I have seen) have been nothing more than entertaining stunts without long term effectiveness. The medium uses words and pictures when it is performing at it's highest peaks.
Do the names Greg Rucka, Marjorie Liu, Eric Von Lustbader, Warren Ellis, or Brad Meltzer mean anything to you? All of them write comics and consider them selves novelists (as does the New York Times Bestsellers list). Alan Moore, Frank Miller and Peter David call themselves writers.
And much as I dislike the term Graphic Novel being used to describe any tradebound comic collection, there are many works in the comics world that go beyond being simple stories, and well into novel territory. The Watchmen is a novel, and you can call it such, or stick the word Comic or Graphic in front of it, but none of that changes its Novel status.
By the way, there's a reason I responded to this post. You reveal your bias against writers in your first paragraph, and the rest of your post is downplaying the writing aspect of comics.
Webcomics are looked at as the bush league of comics by outsiders, and a lot of this is due to the general poor quality of the writing within the field. While professional level artists are surprisingly common within webcomics, professional level writers are not, and part of that is due to the disdain writers are seen with inside the field. That has to change.
Eagle
(I hate writing long posts)