I'm using OS X Mavericks with the Creative Cloud version of Fireworks CS6 and Dreamweaver CC.
When I edit an image from DW, the first time, it works with no problem but, do it again with another image and it appears to work BUT..
In Fireworks, every menu option is greyed out and I can't do anything, except force quit Fireworks. I suspect the problem is the 'use a PNG or this file' dialogue but I can't get to it!
I think Photoshop is an overkill for web design, so there's no chance of me migrating fully, so, I'm stuck.
Try Sketch. Maybe it will satisfy your needs.