Well, the additional slot isn't that big of a deal if we're talking who uses SotD the best
In Dom Urgot is generally played bot; people didn't use to get Manamunes but Muramana damage output is just so high it'd be a shame to not get it now. Remember, Muramana Urgot actually uses all his mana real fast due to the percentile burn so the extra mana regen comes in very handy. You can also start Tear and charge it for about 100 before Minion Spawn which is real nice.
I usually just go Muramana > BC and then get tanky stuff (Spirit Visage or Glacial to hit CDR cap and go from there). Of course, tanky stuff suffers from the rampant armor pen and shred so I'm not sure about the best way to go about itemizing it. And yes, Urgot is of course a very good Black Cleaver stacker.