Dale, and I'm going to miss Lori too.
Unpopular opinion as it might be, she was one of my favourites ):
"Imagination is more important than knowledge. For knowledge is limited to all we now know and understand, while imagination embraces the entire world, and all there ever will be to know and understand." -Albert Einstein
To be honest? I was half tempted to stop watching when Dale died. I was like "How the hell are you really going to go against the comics, THAT much?"
Apparently, the actor wanted to leave [Which made me lose almost all my respect for him, not giving a damn about the fans but just wanting to leave because it didn't fit him.] and the writers were too stupid to recast.
The death was a poor way to write him out compared to the way in the comics. A really poor way of doing it.
As for Shane? He had to go in Season 2, I even knew that. Surprised it didn't happen sooner if you do read the comics.