I use "guys" and "you guys" much as you do. I also am in the habit of using "dude" as gender neutral, but it's a habit I'm trying to break -- although I can hear it as gender neutral when other people do it. Like you, I can't hear "mankind", "he", or "man" as gender neutral at all. There was a Mozilla billboard on Highway 101 for awhile that bore the motto "don't work for The Man, work for mankind", and it was like nails on a chalkboard every time I saw it. I'm okay with "working for The Man" as a phrase, but they couldn't have said "humanity"?