I agree with you concerning the White Nail perk - it's not always easy to consecutively crit-hit 3 times in a row - most bosses move around a good bit, or teleport, or whatever, that makes it difficult (or outright almost impossible) to pull off....the only two easy ones I can think of is Devil's Layer with the tank and the "Big Ol' Purple Ball"....Which, arguably, even on my worst day, that strike is not difficult....