If last beta the problem was Reload Dark Eldar, this beta the problem is boarding party tyranids.
There isn't a hellava lot you can do. Even if you field mass fighters, brace, and hover around your defense turrets, they will get through. You can't let their fighters get close to your ships or you'll lose your defense turrets. You deploy your fighters to intercept their own and you'll hemorrhage fighters much quicker than they will. And the moment either your defense turrets or fighters are gone, or both, they swarm you with boarding parties. Being capable of wiping out entire ships crew, or even two ships, with each boarding action swarm.
If they want to play safe about it, they field 3 battleships decked out with launch bays. You will at best manage to knock out 1 and a half before you straight up run outta troops. And this isn't something you can prevent. Load up on every defensive option possible you are still doomed. And it also makes it useless to field a fleet that isn't decked out with launch bays to defend yourself. Because you will run into a nid swarm player. And you will immediately lose your fleet if you don't at least try to intercept.
I know people were upset that brace made launch bays ludicrously difficult to use but the alternative is significantly worse. Because as it stands no matter how many defense turrets you cluster around you will not stop fighter swarms. Don't make brace as powerful as it was, simply make defense turrets much stronger than they are. If you send a single fighter squad at a Battleship it should expect to knock out only a portion of the defense turrets, not all of them. It should take concentrated and deliberate action to get your assault boats on the enemy ship, not be a default win condition.