I disagree with this strongly.
Difficult content should only be doable by skilled players in good coordination with one another.
That wouldn't change at all. You just have one more difficulty available. If you don't want to do it on an easy setting, do it on hard. Nobody is taking that away from you.
Having difficult content that you can't pug encourages you to get a group of like-minded people.
It didn't. It just gave me one less operation to do and a reason to not continue my subscription. It's not just about finding a group, it's also about getting gear to get there. I'm playing MMOs for 4 years now, mainly SWTOR, LOTRO and WOW - and no, it doesn't encourage me to find a group. It's frustrating to find a group, if it takes hours and doesn't even work in the end, because there's that one tank missing, and the group slowly breaks apart because of it. In every MMO I've played in the last 4 years, I have done this dozens of times, and at one point I've had enough.
It's ok if you like to do that. I don't mind. But this is no reason to not introduce an easier version for the group finder, so that people, who don't want to possibly search for hours for a group, can still do it. That's the whole purpose of a group finder. To exclude just one raid doesn't make any sense. Especially the current tier should be available.
I like this game, but hours of waiting are not fun.