Yes, demo shout as well as sunder armor is very hard to track in WWS.
See this post for the first calculations we made and the assumptions which where taken:
[Warrior] Future of a DPS Warrior
Most WWS we checked out don't have a shaman in MT group, most common is either 2 warriors or 1 warrior and 1 feral druid. It would be interesting to get a WWS parse of a fully "threat" buffed tank though.