If you are able to post things that people actually want to read then yes a blog is worthwhile. However, if you're just doing it because you think it's great for SEO then you're going to be very disappointed with the end results.
All you will end up doing is creating bloat for your website, creating pointless pages because you believe its what google want to see. This is absolutely not the reason for creating a blog. In fact, creating low-quality blog posts on a schedule because your following some SEO guide could actually harm your site.
Every post you do should be link-worthy, that is the true goal of any blog. If you don't honestly believe the post is going to gain links then I doubt many people will actually read it and you are in danger of lowering the power of the rest of your site.
Before everyone jumps on me for recommending you not to have a blog let me explain why a blog could hold your site back.
Most sites the home page is what attracts the most links. This gives the site page rank (yes it's still used internally within google) this page rank is equally spread across all the links from the home page to the receptacle pages. These pages receive their share of the page rank. Having extra pages that are not required or needed will dilute the amount of page rank it has received from the home page. Each page then, in turn, does the same with the page rank getting weaker and weaker the further it gets away from the home page. A page can gain extra page rank if it gains links but if not it is just draining your other pages of the valuable page rank.
A little while ago I was faced with a site that was losing ground yet they were publishing blog posts on a regular basis following to the letter this idea that site must have a blog. The posts, in all honesty, were pointless and not even well written or added any value to the site other than creating what I call bloat. We removed that bloat and also a lot of pages on the site that were not needed.
Over the coming weeks, their site gained places in Google and recovered to where it used to be.
Now don't get me wrong here, having a great blog can help but it has to be great, it should be a place people actually want to read and look forward to your next post. If that's not the case then having the blog could drag your site down.