Indeed. As a super tanky witchblade i was critting over 50k with a mere 600% physical damage (and a lowly lvl 22 guardsman mallet) because of massive res reduction. That is enough damage to clear ultimate, albeit slowly. Although 1000% chaos might easily feel slower in many areas if you lack good res reduction. So the number could vary wildly. Although most of my builds that do ultimate end up with around 1200 to 1400 after counting for spirit.