What makes you think of her as a mere action character?
I don't mean to offend anyone here, but I think that Ruby really is a character that's just there to be there. Ya know, to stir things up a bit.
If not to be so blunt, I would definently say that her character is incomplete. It just isn't the same as the others. It lacks substance (for lack of a better word). I definently don't like the idea of the "gang of seven" very much either. By substance I mean that it doesn't feel right. Ruby just doesn't seem to be an lbt character to me, at least not the way she's portraid in the tv series so far. She could be a very good lbt character if she had an entire personallity change.
She also seems much more childish to me than the others. It makes the others loose their little "Spark".
What I dislike the most about the series is that in mose episodes, there really is only one thing going on. One exception I can think of right off the bat is the big longneck test. In this episode, there were 2 things going on at once, littlefoot being tested, and shorty leading the others to the great stone walkover.