On the balance of senior vs junior staff (only looking at the doctors), let's take a look:
Senior Staff: Kerry (Chief of Staff, hardly ever around), Susan (ER Chief), Luka (Attending), Pratt (3rd year resident -ok, this isn't really senior, but he does teach med students and interns)
Junior Staff: Abby (intern), Ray (intern), Neela (intern), half a dozen med students
Don't know where to put Morris. Technically he would rank the same as Pratt, but I doubt the doctors at County would rank him as a senior!
So excluding Morris, we have 4 senior doctors and 3 junior doctors with med students. It's not too bad a balance, but in the past we had everything from second, third and fourth year residents to attendings and chiefs.
On another note, Carter is (to my knowledge) the only surgery intern the show's ever had (before he switched to emergency medicine). It'd be nice if the show had a new surgery intern who actually DIDN'T switch to emergency medicine and we could see them going through. And we'd also see more of surgery, since that's been cut right back since Romano and Corday left. (I still think the writers made a HUGE mistake when they got rid of Romano. And don't even get me started on how they did it!)