What to do when you are a promised a research-based research associate role but are required to act in an IT support role? First some background. Two years ago I joined a research group as a research associate. My intention in obtaining that position was to publish with the group and build some academic capital, but in the two years I have been there, I have been steered toward support work and software development, and away from research.  I have not been included in any of the group's publications and have had to publish unrelated work on my own. 

I subsequently found out that to justify the Ph.D. requirement for the position I hold, my employers added a few sentences to the job description to suggest that research would be the central focus of the work. Within my group I am seen as a system administrator and IT specialist. This is apparently what my employers really wanted.

I’m also acutely aware that I lack the superior eloquence of my more persuasive colleagues. (This inability would hamper me not only in academia but in virtually any career.) My superiors cannot be persuaded that the system I have been assigned to create, intended to demonstrate (nonexistent) technical capabilities to a skeptical funding agency, has already been executed by several competent, experienced and well-funded teams of more than one person. The project is an all-consuming, deeply anxiety inducing death march for which I am underqualified. Against this, I have at least three competing projects which cannot receive the exclusive, full-time attention each deserves, and I am continually interrupted with trivial software installation requests and technical failures rare enough not to have been documented in the ever-expanding global online archive of technical minutia, to which StackExchange is a prominent contributor. The perspective is that information technology hasn’t specialized in the past 30 years–nothing is too trivial to undertake (except for them) or too specialized and technical to require immersion and consistent practice. It is the menial and urgent work of cleaning digital bedpans.

I don’t have a family or children–I did not want them. I wanted to work in an environment where I could be paid for research. The compensation is $24K less than the administrative position I previously held. I feel that it is self-defeating for me to continue supporting professors, postdocs, and postgraduate and undergraduate students. There is little incentive to promote an individual assigned to projects that provide funding for the group, and to activities that support the research efforts of others, but which are unlikely themselves to result in publication. 

But since my work as a mental technician is valued, I'm wondering whether I might as well seek better compensated employment outside of academia, where I would not have the indignity of supporting persons whose career opportunities are foreclosed to me.
Your writing certainly does not betray a "lack of eloquence"; in fact, it's probably better than most of the computer scientists I know!

That said, as JeffE has indicated, you are being mishandled by your employers, and I would strongly encourage you to find a new position as soon as possible. However, it is important to point out that your situation is not academic versus industrial, but instead good employer versus bad employer. The distinction is crucial.

In any position, there will be parts of your job that are less appealing than others; the absolute "dream job" which you're happy about 100% only exists in Utopia. The key is to make sure that the important parts of your job give you more satisfaction than the less desirable aspects take away. Here, this clearly isn't the case. That does not mean that you can't find what you're looking for, either in industry or in academia. What it does mean is that you need to find it somewhere else than where you are, because it's clear the job isn't going to change in any sort of meaningful way in the short term.