This expansion we have been very closed shop, and have only done raids within our guild with very little (ie zero) outsider input and influence in our raids.
One of the reasons was because of the huge influx we had at the beginning of the expansion. That created a LOT of friction. Nobody knew who anyone was and they weren't really mixing. People complained that the guild felt like it had lots of little cliques in it. It probably did, but that's normal when you have groups of people that know each other. I made a huge effort to bridge those gaps - I knew everyone in the guild personally, I spoke to all of them and made efforts to meet and greet every time I logged on, especially to those quieter ones. However, when I wasn't online back in those days, there would be periods where people didn't speak to each other in guild chat and it made people uncomfortable. I still remember a long term guild member commenting this to me, and saying that their other guild on alliance on their alt was a more enjoyable atmosphere than Frostwolves. It made me sad. I did like meeting lots of new people.
In Mists of Pandaria I felt like it the Saurfang WoW community was a little more friendly. I used to chat to GMs of other guilds who were similar level to us, and it was fun comparing strats, or complaining about GM type things, bemoaning the lack of recruitment or swapping stories of hilarious raid members and our own failings at raids. Three of those guilds did not make it to Draenor. Two of the other GMs I have been a little slack with keeping up with, but they are busy on their own servers doing their own things - I haven't pugged with them for a looooong time.
In the current environment there are only 2 guilds with whom I chat to the GMs. I was eager to pug into their raid on one of our non raid nights, but because I didn't let them pug into ours, they said I couldn't pug into theirs - it was only a joking thing as they had already pulled Blackhand, but I realised that I missed being able to have friends raid in your guild raids. I missed having Exray's friends, Zuli and Mari, coming to our raids. Taxar, who was Luxy's friend, ended up joining us anyway was one of those "friends" who ended up joining us. And it was fun for me having the Blackrock guys around too. Having some of the officers from another guild come play with my guild might have been fun - except I would have to do the "Frostwolves rules" thing that I used to do at the start of a raid just to make sure those guys were in line. All boys guilds can be rather unruly.
Why would I need social interaction outside my guild anyway? It's probably because WoW is winding down. Heroes of the storm is out, and a lot of people are moving off to that to play rather than play WoW. People are playing alts. Bleh. Witcher 3 has also enticed a few people to log off right after raids.
I guess the alternate solution is to just pug into other raids on our off nights. That way I don't to worry about unruly outside influence on our guildies, or introduce elements of elitism into it that people may not find very fun. Also, I don't have to police behaviour - what other people do in their guilds I happily ignore/tolerate (to an extent) but I have rules about what people do in my own guild. Am I being too stifling? I don't think so, I think that public places should be comfortable and I never stop people from mouthing off in private with whatever inappropriate jokes or comments - it's a free country and we are entitled to our private thoughts and be able to share with like minded people. I look forward to 6.2 and the return of some of our players. More people to play with and talk to - that's what I want from my MMO.