Finally finished it last night! Interesting video there.. I suppose they always like to leave the door open.
Did you hear the last little thing after the (loooong) credits too? You hear a crackle, then Isaac's voice call for Ellie.
The final boss fight was pretty easy, when you could just stand in the middle ripping off the necro limbs with your kinesis
Things got less stressful once I unlocked one of the circuit sets for completing an artifact set.. the one that gives you +3 reload/+2 damage. I should have invested in reload speed earlier I was caught out more than a few times, since the capacity for the assault rifle is pretty small, even with a bunch of +clip circuits put in it. Some of the enemy waves were just relentless - didn't have time to breathe, let alone reload!