I quite honestly know very little about nodes, so thank you seth for answering that question haha.
Is psych as content heavy as say, biology?
I can't comment specifically on the Biology comparison (as I didn't study Bio), but Psych is definitely content-heavy. I also studied Business Management and HHD, and it's on par with those in terms of content IMO (if that helps at all).
Does that mean it would take up heaps of time in year 12? More than subjects like chem?
To an extent this'll sound stupid but like, it depends how much time you put into it. It also depends on how much you enjoy it. It also depends on how hard you find it. I don't think anybody can really answer this sufficiently.
EDIT: Yeah, basically what Butterflygirl said in regard to this.