So since the update I have played 10 games of warzone (excluding firefight, which was all I played when the beta was up).
The maps where:
Raid on Apex 7: 1 time
Battle of Noctus: 2 times
March on Stormbreak: 3 times
Escape from ARC: 4 times
Skirmish at Darkstar: 0 times
Now it just might be that I have missed something and Skirmish at Darkstar is not supposed to show up in the rotation for regular warzone and only assault (doubt it). But even so, while 10 games is not a large number to draw statistics from I would expect it to show up at least once. And maybe not have 2/5 of the map pool make up 70% of the games played?