well, they can definitely perform, we saw that in open quali for Rio. In Flashpoint they lost hallzerk, which is about the same as Vitality playing without ZywOo: a disaster. I see Dignitas as a version of Vitality that can actually work: four experienced players supporting a young star AWPer, except these four players have no internal beef and can perform consistently time and time again.
I'm not saying DIG will be top 5 like Vitality were, but they surely can keep it in the top 30 if they actually get to play some tournaments with hallzerk. He's a superstar in the making and having four CS gods around him will only do him good. I'm really excited for Road to Rio.