Such a great improvement in work and a step forward for you as a vector artist, I feel this is one of the best you've done to date.
The accuracy of your shading shapes and bases make it very clear that you are viewing Michael C Hall in the Dexter role which we know and love. You've captured him very well.
However, there are a few areas I'd be tempted to consider working on in the future if you were to do this again.
You've done a great job in rotating the patterns for the shirt and I think this could have also be done with the texture applied to the jacket. Although this element isn't as bold as the pattern of the shirt, every bit counts and helps build up the overall quality of the piece.
You've done a good job with the initial texturing of the hair (representing the strands) however you've not showing any shade/highlights. Consider you've applied shading to the skin and clothing, the hair would also require this to remain consistent with the rest of the vector. You can do this by altering Blend Modes and Opacities of the hair strands.
You've came a long way, don't quit now, you're doing amazing! Just keep working at it! I'm more than happy to give any more feedback should you require it in the future to help you tune your already building vector portrait skills