Sorry, that may have come off harsher than I intended it.Ouch.
Have you seen all the Venus episodes? Her characterisation changes massively (as does her background, it seems). In some episodes she's terribly passive, in others she's a prototype Tara-style independent "swinging chick".
Dr King has one advantage though - none of those godawful songs that stop the drama dead for five minutes in the middle of an episode (sometimes twice!).
I've seen all the Venus eps too (I've seen the whole series, I'm just now rewatching the early seasons in order). At first she annoyed me greatly, but I've softened to her. It is very odd, though, how she goes from being a grown-up but rather naive woman to being basically a teenager, via a haircut and a sudden personality shift. You're right that she seems the prototype to Tara, which might be one of the many many reasons I cannot stand Tara. (Sorry about that too).