According to the patch notes the 1st set of drones will spawn at 29:00, which was previously 27:00. Then the 2nd set will spawn 4 minutes after the last drone is killed. So if you kill the last drone at 27:43, then 2nd wave pops at 23:43. It used to be a 3 minute respawn.

With the intercept node, it will now spawn between 20:00-18:00 minutes left. I think it used to be 17:00-20:00, so they shortened the gap by 1 minute.