So I get that Rollo's Geass causing his heart to stop is a bad thing. But on what grounds does V.V. call him 'defective?' That would be like saying Lelouch's Geass is defective because he has to look people in the eye to use it, or that Mao's Geass was defective because he couldn't turn it off.
Each Geass has its peculiar limitations and consequences. Rollo's Geass stops his heart for an instant when he uses it. That's just part of the deal, right? Calling it a defect implies that Rollo's Geass doesn't necessarily have to stop his heart, but Geass is what it is when you get it; there's no possibility of it being 'better' or 'worse.'
Unless of course Rollo didn't obtain his Geass under the same circumstances that Lelouch, Mao, and the Emperor did.