Argh, sorry for the delay I wrote up a great response but the Moz system ate it and then I was in client meetings. I'll try to summarize it from memory.
It sounds like you want to know if WordPress is worth replacing DW with. From what I can see you've got 3 choices:
1. Do it all manually in DW as you are now. Pros: Familiarity, total control. Cons: Time of maintenance, time of creation. Also less functionality for moderation, comments, etc.
2. Do normal site in DW, blog in WP. Pros: WP will automate posting dates, categorization, comments, trackbacks. Cons: You have to learn WP. You have make a WP template in DW that matches your current site. Two systems to maintain.
3. Convert entire site to WP. Pros: All in one solution. WP will probably help automate mundane site tasks you do manually now. Cons: Loss of total control, WP run-up learning time, WP template creation time, possible SEO implications if sitemap/linking structure changes (positively or negatively)
If you know you're in this for the long haul, and the blog is going to be fairly active I'd suggest #2, with an eye to going to #3 when you're comfortable, or deciding on something else if you decide you hate WP. WP is very easy to maintain and create content for, but it's not a fit for everyone (see my final note). The hybrid approach of #2 lets you get familiar with WP, make a template for it, and see how Google indexes content published in it, without having to commit to having your entire site on it like #3.
Final note: Speaking personally I'm not super comfortable with WordPress because it feels like every 3 months or so there's an exploit that hits nearly everyone. I've worked with it and maintain current installs, but that's always at the back of my mind when considering it for a new project.