Your rankings make no sense to me. I don't understand why you deem someone who has separate social circles inside and outside of work as "less healthy".
God forbid you run into issues with your outside social circle, you've still got your work circle, and the other way around.
I've only had option #1 happen once, and it was when I encouraged a few friends to apply at my company, and even then, it didn't really merge the social circles, I just had some people which were in both. I wouldn't do it again, either.
It's great to have multiple groups of friends, they don't all need to be related through work.
It makes sense in a way, when you spend 7+ hours a day with those people, you're bound to find some common interests that could bring you closer. What's hard is maintaining those friendships once they're no longer coworkers, as usually those "common interests" are mostly about the company's.