In the interest of full disclosure, I'm the author of a commercial (".resx") localization tool for Visual Studio developers. I won't be mentioning anything about my product here though so as not to violate the site policy.
The program is a Visual Studio add-in that developers use to extract all strings from their ".resx" files into a single, proprietary file for shipping to their translator. Their translator can then download a free program from my site (no cost to them whatsoever), translate the strings and send the file back. The same add-in that created the file in the first place is then used to import those strings back into the programmer's solution. To this end, the application does many things that will presumably solve your "workflow" issues. It was designed for this from the ground up.
For instance, if a programmer changes a string in their solution, then their existing translations will require updating of course, so the program will flag them for review. This means that the next time they ship their strings to their translator, the translations will be highlighted in red, meaning they need to be reviewed and updated. The program also has many other bells and whistles, including a lot of error and consistency checking. For example, if a programmer changes a string in their solution while it's out being translated, it'll be brought to their attention when the strings are later returned.
