I haven't had this problem as far as a low hub score most of mine are fairly decent - low traffic issues can be remedied often by some rewording and using the "title tuner" tool as well. It isn't always feasible, but that little tool has helped me get a couple of hubs going again.
If you have a low hub score I would recommend a rewrite - or at least some revisions and maybe adding some original images or links to helpful resources as means to give the hub more value to the reader (and a higher hubscore) You may want to expand on your subject - or if your topic is too broad perhaps narrow it down and tightly focus in on a "niche" so instead of "Crochet" in general for example you could focus a hub on a particular stitching technique... more targetable that way by search engines. Subjects that are too broad get lost in the ocean of other info out there.
Also, backlinks are important and self-promotion - but NOT in a spammy way ever. You can answer questions on question sites that relate to your hub. After answering the question thoughtfully with a thorough answer leave a link to your hub. That works well to get viewers for me that actually read the hub, thus increasing the score. Also, hubs that rock will get people sharing them via facebook, twitter, and stumble as well :)