Orchid is great. I ignored it for a long time but finally got back into it. I like it over Morningrise.
About the mainstreamness.. you know, I think BWP has less "proper" song structure than Still Life. Thinking back, about every song on there has a chorus (at least musically) halfway through that repeats near the end. Though the songs are so long it's hard to notice that much. On Blackwater, there's more of an endcapping thing, with a beginning part repeating at the end, like in Leper, Drapery, Funeral. I think one of their most mainstream metal songs is actually the title song on BWP, despite being 12 minutes and ending in a completely different place from where it starts. Beside the interlude (Only the hyperactive people can't get around that), it's just pure groove-laden death metal.