Arambai die hard to Ballistics Crossbow and Skirmishers because the Arambai has bad pierce armor, terrible range, and takes more bonus damage from Skirmishers than foot archers. Maybe instead of trying to play a standard booming game when you know what’s coming, your team first prioritize defensive Archery Ranges, especially fast Ballistics. Arambai is not any different than other super-aggression strategies where surviving the initial push ought to always mean a big and long lasting economy advantage for the defending player. And I doubt the Kmher economy is strong enough to outboom 2 players.
And if all this still doesn’t work, then I’d have to see some recorded games of this invincible strategy.