We tried to run one of these today on Everlasting, and everything went completely sideways.
We did manage to get 5 teams of level 35+ players who all had the badge. Even with double the number of players on the server today, I've had MSRs in the RWZ fill faster on a weekday at 1pm mountain time. When we did finally launch via the queue, only half of the league actually managed to load in. The rest either crashed or were kicked back out to KW, where we were launching from.
On Everlasting, all the regular MSR leaders have pretty much agreed to avoid the trial completely at this point and just run in the zone like normal. This of course means we spend around 5-10 minutes shouting in broadcast to get people to leave the zone so we can get the full league in, but even that is less hassle than the trial version is at the moment. The zone also lets us bring in lower level characters, which makes it much easier to fill a league.
The Trial just doesn't work. The easiest way to fix the problem that caused the need for the trial is to just bump the player cap to 60 on the RWZ. It's rare for there to be 10 players who aren't in the league in the zone anyway, and it wouldn't allow an excessive number of extra players being brought into the raid as an overflow team.