I doubt that a degree will make you more marketable. But you can learn many things that will advance you way beyond being a .NET web developer. Unfortunately,

I doubt that a degree will make you more marketable. But you can learn many things that will advance you way beyond being a .NET web developer. Unfortunately, recruiters will never tell you why you missed out on a job, so it is extremely hard to determine whether your lack of a degree is the reason for missing out on a job or some other factor. In my experience, solid experience trumps paper credentials. In companies where that is not the case, you have to ask yourself whether you would even want to work there.