IMHO, there're too many subgenres of metal in existence, which makes sorting bands a mission impossible. For instance, it would be enough to list My Dying Bride just as Doom Metal, not Depressive Doom Metal or Gothic Doom Metal!
My Dying Bride is a Depressive Death- Doom Band that a huge influence on Gothic Metal. Many of the original Gothic Metal Albums were produced by band with roots in Death/Doom.