Anyway , I think those black/death/doom metal guys went to these evil kinda lyrics cuz their pissed at overused lovesong kinda lyrics , not putting in mind that their vampire (and all other bloody stuff) lyrics have become overused too !
These evil lyrics usualy don't reflect those who are writing it or have an impact on most people who read it (cuz scary lyrics sounds like scary granma kid-tales ;) ) while lovesongs are more grown-up lyrics.
The point is, nice overused lyrics are definately better than crappy overused lyrics.
So, if you want your lyrics to sound unique , you don't have to be scarry (cuz it's not unique anymore :D ) , you just need to find some newer non-categorized topics.