Well, you're right about the fact that the writers failed to make her interesting. It's not her fault AT ALL! Not even a little bit! She came in, did what was asked of her and did an EXCELLENT job with the crapfest she was given by the writers/ptb.
well, you never know what's going on behind the scenes. to put all fault on the writers isn't reasonable, imo. i wouldn't put fault on anyone, really, since we don't know the facts, only what has been released to the press (which, let's be honest, is always censored.) maybe LLS was a queen of all divas or decided to have a joint break every 10 minutes. lol
but i think you kind of overemphasize the importance of old characters. i mean, most CSI viewers are people who want to watch a good show, a puzzle, and twisty storylines. i think it's usually women who
really like Nick or Greg that are the most bothered. the fact that Ray has a lot of screentime doesn't really bother me that much. i don't notice it, tbh.
in my opinion it's the fact that this show is 9 years old. using almost the same formula every episode is repetitive. to make it worse there are 2 more shows with the same scheme (to add it all up we have 21 seasons of CSI shows. 21x23= rougly 483 episodes). in how many different ways can you kill a person?
those 2 more shows have a bunch of other actors and they are doing almost as good (or bad) as the original. i think CSI was always doing it all a little better hence bigger popularity, but i don't think the ratings drop is caused by Greg or Nick getting less screentime. they've never been the front people, anyway. now Catherine is a different story and her smaller involvement might have some impact.
there is one more thing. don't y'all think that maybe the actors themselves are not too eager to have a bigger workload? i mean, they get the same paycheck regardless and after 9 years on the show i doubt they would want to hog the show instead of letting LF develop his character. that was a case with Gary Dourdan in S6 or 7. i heard he wanted to do other projects so he asked for reduced screentime. and then a lot of people complained that the writers ignore him.
ETA:
which reminds me of GE's back problems.