No we saw mercer being a necromorph, as soon as that video ends you walk back into the main hub and he is one being turned right as you enter in front of the door.
The hallucinations were caused by the marker not the hive mind, and wasn't the marker on board when Kendra was going to escape before she mopped up the floor?
Apparently if you turn in the marker before every necromorph is dead around you it kills them, so I'm guessing that if she was a necromorph she would have died when you returned the marker. It's just the way she made it sound it made it seem like she was committing suicide and she'd know what kills her. The only thing that would make sense is for her to be an illusion at the end as well. Even if not Isaac can't die, he has the Isaac Boot Stomp which has to be the most power attack in the game.
Tag(thx fkusumot) - "Yet again I completely fail to see your point..."
HD vs Wii, PC vs HD: http://www.vgchartz.com/forum/thread.php?id=93374
Why Regenerating Health is a crap game mechanic: http://gamrconnect.vgchartz.com/post.php?id=3986420
gamrReview's broken review scores: http://gamrconnect.vgchartz.com/post.php?id=4170835
