It's up and stable as far as I can see, and there are thousands of players connected to it.
I can only guess there is some sort of network interruption between you and the server somewhere. If you run a WinMTR test to sao-m.speedtest.pathofexile.com, I might be able to see where that is and check if I can fix it.
It’s a little bit of a myth that Legacy League would be really easy to bring back. It was made for Path of Exile when we had three difficulties and would need to be updated for the single play-through experience. This was also many leagues ago so there would need to be lots of testing and work to implement the leagues that were introduced since then. We would also need to retest all the old leagues to make sure they work nicely with existing game content. Additionally, almost all past league content is already part of the core game (like Delve, Incursion etc). At this point, it’s about as much work as a league made from scratch. It’s not off the cards that we’ll do something like this again in future but it’s unlikely to be something that we quickly whip up.
with other skills or movement
So what about holding down the mouse button with Flickerstrike? Can you prematurely cancel the third strike this way?
If you are just holding down Flicker Strike, and not doing anything else? No.
There have been a few bugs where certain specific skills had bugs with Multistrike which caused them to not gain the damage bonus (e.g. Lightning Strike projectiles), or consume too many charges (e.g. Flame Dash). Basically all of these bugs have already been fixed.
But there has been some confusion about how well Multistrike has been working. Of course, generally speaking Multistrike is supposed to allow you to cancel out of it with other skills or movement, but afaik it has never "self-cancelled".