New
The start of the series -- from Farpoint until at least the midpoint of Season 1 or so -- had to establish a lot of things, and first and foremost it had to establish this new, more (than TOS) futuristic landscape.
So there were a lot of things designed to shake things up:
1) Picard's first action in the pilot, basically, was to surrender ... which of course Kirk would never do. It's a "who is this new captain and wtf is he doing" moment from the start to help say there's a new (star) sheriff in town, so to speak, and a kinder, gentler one that the swashbuckling Kirk that everyone was accustomed to.
2) There's an android on the ship in a prominent role. A dude who can't see, only he can, thanks to his fantastical futuristic Google goggles. A freakin' KLINGON is on a Federation ship, and he's not a prisoner or an occupying force. An empath, even a KID for goodness sake.
3) Tasha fits into this -- a female security chief is a new twist and a signal of a 'more advanced' society as well as something to challenge conventional thinking and set TNG apart from the previous ST incarnation (both on TV and film).
So all of these things are part shock value (especially Picard as Captain Surrender Monkey) and 'hey, this is a whole new ST universe.' Yar is just part of that tapestry, and what did and didn't happen with her character going forward shows, to me, that litttle thought was put into her and some of these other things beyond 'we have to make clear that this is a different ST.'