as @emraldis said umbrellas .... aa was able before but has been changed .. maybe cause to powerfull i imagine flak wrecked unitcapsules ...
don't use aa, use a swarm of like 20 fighters. That''ll take down an astreus in a second. EDIT: I misread. Just use umbrellas, make them particularly dense around places you really don't want a bunch of slammers landing.
You have no idea how correct bengeocth is on this one. I didn't have enough umbrellas one game and an astreaus fleet of at least 400 (Not even exaggerating) dropped, trying to drop a thousand vanguards/slammers/sniper bots on my poor little nemicus. I had so many fighters... Not a single one landed