With the cove coming back and just around the corner I decided to get my hands on a set of mournlode weapons. Off to house C i went!
Some time later i finally got my hands on 1 and went to test it out. I noticed my to hit bonus and damage wasnt what I was expecting. With the righteousness and greater undead bane i was expecting an additional +6 on the weapon against most undead, for a total of +11. I wasnt seeing any of that.
To test this a bit further i hit up the AH and bought 2 items, a +1 heavy mace, and a +1 heavy mace of greater construct bane- Then proceeded to my guild ship to smack that dummy around a bit. Tested both weapons. Same damage range (just the bludgeon damage, not counting the 4d6, that seemed to work fine enough), same attack bonus. No +4 to attack or damage when using the greater bane weapon.