To have stents or not, should be the physicians decision in regards to if the malformation or such requires it. The fact that your doppler does not find anything, it would appear to my untrained thoughts that the angioplasty did have some staying effects (guessing there were issues the first time). But my personal perspective, I would be REALLY hesitant to get a stent, especially since your improvements were minor at best. By the way, I did not personally experience any real improvements I can pin down, and I have had 3 treatments.
Each time, I specifically chose a different dr, in case they could "see" different issues. My final decision was to give it one last try and I went for the best physician I thought I could find. I would not only suggest, but recommend you get a treatment performed by someone who not only uses, but has extensive experience with IVUS for CCSVI.
I had a doppler in Australia before my last proc, and they found nothing. The doppler in preparation for my last proc done by Dr Sclafani they found an issue (or two) by doppler, and he found a number of issues in the procedure using IVUS that the other two had missed using a flouroscope only.