I think it's also about Oda's being inconsistent, because on the one hand, as
@Cross_Marian said, HK kinda did their job and would've succeeded if not for Luffy, Loki, Zoro and Sanji.
But at the same time, they had really plot convenient DF powers, and I struggle to imagine, say, Sommers against Queen or Killingham against King, with Queen and King really struggling against them even with their regen powers. Or even if we go lower to Tobi Roppo level, Ulti would trash Killingham imo. Sommers probably would be more impressive.
Dragon panel tho brought our expectations that HK are above YC levels, but they are not, and that makes me worry about Revos actual strength.