I don't know about "now" as I don't play on PCEU anymore, but last year there were at least 2 organized (voicechat), decently successful EP ballgroups. (EDIT: clarification - in the main CP campaign)
One was The Anomaly, which I used to raid with for a couple of weeks - until I left PCEU permanently over the ever worsening server performance.
The constant group crashes aside (due to the game server being trash), they were doing quite well at the time I left.
There was also another EP voicechat ballgroup at the time, also decently organized and fairly successful - unfortunately I forgot what its name was, I was never part of that group. All I remember is that the leader was @Julibomb.
Of course, at the end of the day, talking about "successful" is a moot point when the game is literally unplayable, abilities don't work, and you crash every 10-15 minutes whenever more than about 2 enemy raids show up - and then you spend another 10-15 minutes at the login screen staring at the error messages.
Ballgroups are one of the leading causes of lag, so have at it.
I'd say bad programming is the cause of lag. Or the bad handling of synergies and buffs. But that's not the topic here.
I'm just asking for them.
Another one, that I know: IV Imperial Legion BM
amazing good, wipes Illusion in seconds^^
but only russian speaking