Has Niantic finally figured it out....
.... that high level raids need to take place where people play? For the second time since Sunday there has been a legendary raid in the city in the most popular park.
My first legendary raid was 3 days ago, I could not catch him (but my son did). So now, same place and time, there was yet another Suicune raid and this time I got him (first throw, golden razz, no curve). I had asked my son and that's what he did!
I proudly present my first legendary (82%, but who cares?)
What's funny, ever since legendary raids started, I had been going to this park (10 minutes from work, in the summer there were still raids although I work long hours) and there was never a legendary (or even t4) raid, and now 2 in a row? This can't be coincidence. Like I said, maybe they're finally figuring it out.

Answers
We still get those weird ones (e.g., remote forest trail), but it seems the popular parks are getting more of them now. Or maybe it's just RNG.
It's amazing how many people are actually playing this game - it's great. Everyone coming together for those high level raids. Of course, this is no news to most of you, but for us rurals (or late bloomers, LOL) it's truly amazing.
I got another Discord invite, this one team specific. I'll be happy to let everyone know that I just kicked Valor out of "my" gym (near work) again :)
No they haven't.
I can't comment on highly populated areas.
But in my small rural town with 2 arenas,
the kind where a weedle can stay up for days before somebody driving through town decides to stop for a min and take it down, I've seen and increase in T5 raids as well.
Since the release of Ho-oh, I've seen more T5 raids than T1, T2 and maybe even T3 combined. With only one or two T4 raids.
It can be a coincidence.
This morning there were 4 Ho-oh raids ending by 7:15am in my neighbourhood; three of those gyms were places that I had done Legendary Raids in the past week. (Two were less than a block apart, and on the first night of Ho-oh about 30 of us did raids there back to back, with many of us using double-phones (for me, it was mine and my wife's phone as she couldn't go out that night), so could have been upwards of 40 accounts playing. Amazingly, I caught 4 Ho-oh's that night - two for me, two for my wife, on only 2 raids. Is anyone else finding Ho-oh that easy to catch, or did I just have the best luck I've ever had with PoGo and the best luck I will ever have?)
The only gym that had an Ho-oh raid that was unusual for it to have one is a gym that is really hard to get to in cold weather... but could technically be considered a park. But it has raids pretty much every day, and I've done at least 1 Legendary raid there in the past (back in the summer).
So yeah - it's probably just coincidence. I'd LOVE to be proven wrong, though...