Photoshop isn't even used much for visual design these days: it's all pretty much Illustrator. Vectors make dealing with resolution much easier, but redlining is still needed when rasterizing to lower resolutions.

Most of the designers (outside of web to be sure, since I don't live in silicon valley) I know don't use textual formats, that is for developers. Much of the content is too dynamic to work with textually without substantial programming.