Instance: Hall of Lightning (Heroic)
DK+4 ele shammies.
Just would like to add to the above, that with unholy Dk tank this instance isnt half as hard as with a pally. For LOken I can actually stay in for first aoe lightning nova thing, and just use my anti magic zone on my team, by the time he does the next one hes at 20-22%. Similar thing with 3rd boss, Im actually able to stay in for one or two of those.