As someone who has done a webcomic - it's a lot of work. Even just the writing part, though the art definitely takes up more work. And yeah, don't expect instant success.
To suggest making a webcomic that has someone else do the art (the harder part of the two, mostly) only works if you're Penny Arcade. But yeah, the "write thirty strips" is a good point to be made. I have about that many scripts kicking around on my hard drive, and it can be tough to do.
Why you need someone else to do the art, I don't know. Order of the Stick isn't great art, after all. neither are a bunch of other webcomics.
Mine, for example, works fine, and I can't draw to save my life.
Make sure you have at least four hours a week to work on your webcomic. That is what's killing mine right now - I just do not have enough time to devote to it... so it's sadly on hiatus for the next few months.
I would make your world/setting as broad as possible, so you have more fuel for mockery, and set it up to parody some 4e tropes without it being a complete rip off order of the stick. The
DM of the Rings is a great webcomic (and where I got the inspiration to do my own), and I personally find it's funnier than OotS in how it's implemented. But try something even a bit different. I think it could be fun to do something like "how to survive now that the edition has changed" and run the story as a sort of "4e survival guide" for newbie adventurers.
It'd be really funny if the adventurers' guide knew about the rules of the world, but not that they were "rules". For example "Studies have shown that those who use a heavy shield are approximately 5% less likely to get hit by an incoming attack, regardless of the percentage of increased surface area the shield has over a light shield. The discoverer of this effect, Louis 'Two Fingers' Malloy, was quoted as saying "I wish I knew about this three fingers' ago!"."
Or something like that. I'm riffing, here.
All that being said, remember that success in comics (indeed, most things) is just saying "yes" one more time than everyone else says "no". Best of luck to you!