Blizzard has implemented another handful of hotfixes, and this set includes a couple of fixes for Rotface and Festergut. Here's the list straight from Bornakk's post:

• Deathbringer’s Will trinket will now proc haste as a replacement for armor penetration.
• The val’kyrs spawned by the Nibelung staff will now always hit with their smite attack and their damage has been increased for both normal and heroic versions of the staff.
• The chance for the proc to activate on the Black Bruise weapon has been increased.
• In the Rotface encounter, big oozes should now properly combine.
• Rotface’s acidic blood and Festergut's acidic blood now function appropriately through the use of the group looting and master looting systems.