As facts seem to point:
- Red John is most likely a man
- Red John should be older than 30 years

the last would left out Kirkland and Partridge, but
Patrick has a list of 7 suspects, seven as the number of letters in "Red John":
what if John is not a person?

Could be that all seven suspects are Red John, being that just a fake character used by all of them,
That would explain why it has been impossible to find any coherent clue on all John's murders, Partridge and Kirkland may just be the latest members of the "club".