The Murrays were perhaps one of the last good family units introduced in Brookside. Diane did get on my nerves a bit but she was well acted as was Marty. The three kids and the nan were well cast also and together they all worked well. The bullying and pregnancy/abortion arcs were very well done even if dragged out a little
One of issues I found with Brookside in it's later days before it went majorly downhill with the introduction of the ill-fated Gordons, Bernie Nolan quitting and the hostage/helicopter rubbish was the seeming refusal of the producers to clear out some of the longer established characters when new material for them dried up. As all the characters had to live either in the six houses or above the shops Brookside didn't have as much scope for a large cast compared to say Emmerdale, Eastenders etc.
The Corkhills, Dixons, Farnhams, Shadwicks, Rogers, Johnsons were great families in their time but I really feel that as these families dropped numbers the strategy was either returns or keeping one character on with much lower story potential.
Bev and Josh were reintroduced alongside Ron, Mike and Rachel but storylines went around in circles - Mike & Rachel moaning/bickering for years struggling to get by financially, Josh being a troubled teen even though this role was played out by Tim before him. Any new material that involved new characters e.g. Anthea and Ron's long lost daughter Megan was abruptly wrapped up to shoehorn Bev back in and it was really more of the same from her. Jacqui jumped into the Farnhams even though she couldn't stand Max for years and literally replaced Susannah overnight, which stretched credibility. Sammy returned and caused nothing but grief for Katie, which we'd all seen before. Emily became extremely unlikeable and everything between her and Tim becamse very tedious with their ongoing schemes. Her grandmother Jessie then followed suit with crazy behaviour and the relentless belittling of her husband.
The only time any established character seemed to leave was when material for their character became completely ludicrious and was generally of their own accord e.g. Jackie Corkhill, Lindsey Corkhill, Sinbad, Susannah Farnham. Mick Johnson might be an exception as I can't recall what story he had prior to the actor quitting.
While I completely recognise that long standing characters are needed, I do think moving some of the above out would have help rejuvenate the neighbourhood and replace them with well planned and thought out families, which the Murrays were but the Gordons were not. There were others that weren't used properly possibly because these senior characters were given the material due to their loyalty to the show e.g. Lance & Leanne, Nisha, Cassie, Mo Magee, the new doctor & his wife.
Yes crazy storylines were the final nail in the coffin but cast mis-management I believe played a part as well. I do miss Brookie - there were some great years