One thing about what you are doing, is, you are showing that you are active in enhancing your skills and gaining experience, which I think is great. I instructed full time before I started flying airliners, and to be quite honest it gave me alot to talk about in my interview for my current job with some of the awkard questions, as well as gaining alot of flying and people experience.
Personally, and this is only my own view, I do not think it is necessary to do a JOC. I would save your money, and put it aside for something else, maybe even simulator practice, should you get a simulator assessment. You could argue that doing a JOC will give you those essential handling skills, which is true, but 6 months or a year down the line, you will be out of practice if you were lucky enough to be offered an assessment. Just a thought.
All the best with it and good luck.