Use each application for what it is best suited for.
Illustrator is great for drawing. Fireworks is great for Web layout and Web graphics production. Dreamweaver is great for HTML and CSS coding.
Fireworks can open Illustrator files...with come caveats. Personally, I only import Illustrator graphics into Fireworks if they are something more involved than Fireworks can do, for example, complex shapes or text with alternate glyphs in OpenType fonts.
If you just need a quick prototype, then Fireworks code is good enough. Fireworks is a Web graphics and prototyping application. It is not a WYSIWYG Web page layout program. If you are going to build code and you have Dreamweaver, you are better off building code in Dreamweaver, as Dreamweaver's code is more robust.
Also, unless you set it up very carefully, the code Fireworks exports is really ugly and difficult to maintain. In the long run, you save yourself frustration and effort if you use Fireworks for graphics production only and Dreamweaver for coding.
Well I wish Fireworks was a WYSIWYG website creator.
Or that Dreamweaver was more WYSIWYG than it is.
I find DW needlessly obtuse. (Compared with just about every other app that Adobe makes)
(This is the part where all the web coders out there pipe in a give me a lecture on the true nature of web design and how web design isnt for the faint of heart or people who dont like coding)
Also DW has its origins from Macromedia. They always had a different vibe about their products.
Oh well, just "blue" skying here...
Maybe some day Adobe will actually make a WYSIWYG website creator and the world will be a better place.
(Or maybe Apple will. : ) )
Fireworks does seem pretty powerful and it can create web pages.
It's just what you do with them once they are created that remains a bit of a grey area...
You can have a WYSIWYG editor for print and PDFs, because the intended final output will formats are pretty nicely locked down.
With the Web, your final output has to be markup language and, sometimes, code that is interpreted and rendered by a browser. Oh dear. Did I say "a browser?" Silly me...multiple browsers, each with their own capabilities and quirks about how they do things.
Yes, there are WYSIWYG Web editors out there (even DW in design mode), but you can only do the most basic stuff with them or risk your markup and code being bloated, wonky, horrid, malformed, and badly-rendered.