I am 32, recently passed the CPA exam, and am 4 classes deep in my MST program. My undergradute gpa is just under 3.0 and my MST GPA is over 3.5.
I went to the career fair and found that maybe only 10 out of 30 firms will take unexperienced hires. The 10 firms that will take unexperienced hires are the Big 4, large nationals, and large regionals. These firms mainly recruit out of their internship programs.
So one strategy would be to take a couple classes the semester before the job fair and a couple during the semester job fair and apply to internships. This was my strategy and I am convinced that if I don't get an internship my chances of getting value out of my MST program are slim to none. I mean the IRS isn't even hiring these days.
The other problem is that MST programs are expensive. I have not found a cheap online MST program with good campus recruiting. Most MST programs are close to 30k.
Its also worth mentioning that if you already interviewed with some of the larger firms for audit you will most likely not be called back a few years later for tax. If the larger firms interviewed you and did not hire you it was either because your interview skills were not good or they didn't feel that you would fit in with their culture. These firms are efficient and reinterviewing people is inefficient.
It is very possible that you are not great at interviewing, since it sounds like people do call you in for an interview based on your qualifications. If this is the case then your time may be better spent reading interviewing books, improving english or grammar(i have horrible grammar and its on my to do list), and working on your body launguage.
I am one or two interviews away from giving up my MST program and the 13k that I have invested in it. I would not recommend pursuing the MST for job fair access unless you are naturally personable and have a tract record in those kind events. It also important to mention that state accountancy boards and the AICPA host functions where you can meet firms and this is a much cheaper way to network. Your state board should also host networking functions and this will be a great way to improve your interpersonal skills.
If you are truly interested in tax then I would get a job at HR block, pass the EA exam, get quickbooks/excel certified, and apply to public accounting firms next recruiting season. This will be my plan if I don't get an internship. Because if a person with both a CPA and EA who is fluent in quickbooks and excel cannot get a tax job then the barriers of entry and current demand do not warrant investing 30k in a masters program.
Passed all 4 exams in 2014!