For me, this encounter felt reasonably balanced. Difficulty curve where i would expect. Good variety of enemies for this rating & something to keep everyone busy. Could be punishing for the less experienced 'run & gun' type player. The enemy density was good like the impression that they were constantly defending the site. Enemies spawning at a distance and navigating towards the players is what adds immersion to the situation. Much better feel than just a constant static spawn, clear, spawn again cycle from the same locations.
Now, the Rocket Drone. This was the exception - either drop the rocket drone health value to the same as the Seeker (for a fast kill) or reduce the damage from their rockets & their reload time. When Rocket Drones are 2 or more, they tend to group together and end up simultaneously firing at players, essentially causing a double damage (or more) effect since they are tracking & targeting times begin to all converge when they see the player. Taking multiple bullets or clips to destroy while dishing out "stacked" damage is painful.
