Possibly, but also possibly not. You could argue that self-defense will lower homicide rates only when enough of the population owns guns to actually start deterring people, and that high gun ownership states still don't have enough guns to lower the homicide rates.
I've posted this link a couple of times over the past week wondering if people would see the underlying reason as to why gun related incidents are almost non-existent. And it's not just the regulation.
You've probably seen this, but http://slatestarcodex.com/2016/01/06/guns-and-states/… was great. The key question is "what factors are you controlling for?". Naive graphing is largely just going to pick up an urban/rural divide without giving a good answer.