Yes, But DS replaces OB, And it doesnt consume diseases.
what he said. with ob being taken off of might of mograine you lose the 45% crit damage bonus. ob will crit for about as much as hs. ds self buffed i was getting 7-8k crits regularly and raid buffed in ulduar with shirt of uber was getting some nice 11-12k ds crits using the 51/2/18 spec. glyphs you want are Glyph of DS, Glyph of DRW, and Glyph of Dark Death.(15% more dc damage)