Firstly, I must say I did not find this, I take no credit for it.
There is a weird pattern in the TV series that I would like to share, these are the main characters that have died in the TV series so far:
Shane and The Governor are the only exceptions. (Note, they are the only antagonists on this list.)
Sophia didn't appear in 'Secrets', and the 4 episodes before it, but died in 'Pretty Much Dead Already'.
Dale didn't appear in '18 Miles Out', but died in 'Judge, Jury, Executioner'.
Lori and T-Dog both didn't appear in 'Walk With Me' but died in 'Killer Within'.
Merle didn't appear in 'Prey', but died in 'This Sorrowful Life'.
Andrea and Milton both didn't appear in 'This Sorrowful Life', but died in 'Welcome to the Tombs'.
Hershel was pretty much absent from 'Dead Weight' apart from a small cameo at the end, but died in 'Too Far Gone'.
Take note of this. It seems if someone is absent in 1 episode, they'll die in the next one! :D Unless they are an antagonist of course.