Yeah i selected the brutal in the selection, but i think it might be because i default my difficulty to "Brutal" in the editor so it gets set before your map sets the difficulty.
Edit: I'll pm you a vid of it in a few.
I played them and recorded some footage without any commentary that i will upload later, but i found game breaking bug on mission 3 when playing on brutal.
It's on the spawnWasps Trigger that generates new workers for the enemy, when you play on brutal it generates them every 0 second. I just changed the value to 200 and it worked.