I'll begin by saying that I didn't pick the mission! My opponent, running Hunter Clade, was banking on winning the roll to decide who attacks/defends. He did not, and so a Martian kill team was ambushed by the Kounta Krumpaz on a desolate battlefield in the Octarius sector! Notes about the game below the cut.
First of all, I'll point this out if you don't already know: even if your Kommando is a specialist in their field, it doesn't assure victory in that field in the way an Intercessor in their lane (moisturized, unbothered, etc.) will. Kommando players have the tools to match any opponent in any field, but they need support! Lock up enemies in melee with a Kommando Boy before charging in with a Slasha/Breacha, force the enemy to deal with your gunners while your melee specialists get into position, spread out your APL boosters so regardless of flank the enemy has to deal with extremely mobile operatives! You'll be bringing 10 models on average and you need everyone to do their job to secure victory.
Second, boy howdy did I ever underestimate the Sicarians. With Neurostatic Interference in play, even Ork melee specialists find their effectiveness blunted with their rerolls removed. If you must fight them in melee, brace for losses and make them pay in other areas.
Third, being the attacker on Ambush is absolutely an Ork specialty. I had my Breacha Boy tucked under a ruin for the better part of three rounds, only emerging to blow a Sicarian to pieces with a bundle of Ork-packed TNT. My opponent, in the meantime, had a squad with three heavy guns that couldn't move and fire in the same activation. If our positions were reversed (or he wants a rematch), the better play would be to form a gun line with the heavy gunners, give the lot of them up for dead, and plant rounds in any Ork that pokes its head out to nip at Martian heels. Between plasma, phosphorus rounds, and the hellacious transuranic arquebus (hitting on 2+, dealing 15 wounds on average!), assaulting a covered Mechanicus operative on open ground means almost certainly a one-for-one trade at least. Instead, the AdMech was bottled up at his half of the board for most of the game trying to minimize losses.