ok first of all, just because you didn't mind death metal/vox the first time around doesn't mean the majority of people who listen to it for the first time didn't. what is the most common description a non-metaller would tell you about metal? "the 'music' is nothing but noise, and what's up with that singing? its nothing but screaming!" and most of the time they are only talking about "weaker" bands like to use someone's examples LoG and trivium.
second of all, most of orchid, morningrise, MAYH is death vox. sure morningrise has to bid you farewell and other moments of clean singing, but most of those three is death vox. those threee albums alone easily outweigh the all cleanness of damnation and the "some" cleanness of deliverance.
but to contribute to this thread i would introduce them with mainly sabbath.