Idk what the hell WR KK is unless you're talking Ryu but 66kkk is not more damaging than any set up that ends in pp6pk for Hayate. 8k, 8p, pp6pk is much more than 66kkk and h3pp, pp6pk while harder is much more than both.
But that's the thing, the more efficient combos end in pp6pk. Let me get 8p, ppp, 7k for simple damage and allow 8p, pp6pk to be his wall oki set up.