So about Kaido seeing the silhouettes....it's very difficult to believe Luffy has better haki than BB, Mihawk, Dragon, Garp etc.
Its more so that Kaido has a list of people who can legit hurt him and actually did it in an encounter. The Scabbards were cutting the fuck out Kaido, impaled him and even had him on his knees clutching his wounds. He had a vision of Oden when they attacked him. However, he could quickly recover from it and expressed his disappointment that he was wrong.
Luffy on the other caused LASTING damage on Kaido just like Oden on panel. At best, it says Shanks has the best haki out of everyone alive.
Its more so that Kaido has a list of people who can legit hurt him and actually did it in an encounter. The Scabbards were cutting the fuck out Kaido, impaled him and even had him on his knees clutching his wounds. He had a vision of Oden when they attacked him. However, he could quickly recover from it and expressed his disappointment that he was wrong.
Luffy on the other caused LASTING damage on Kaido just like Oden on panel. At best, it says Shanks has the best haki out of everyone alive.
Other top tiers can hurt him but seems like Kaido clearly put those that can actually fight him (whatever that means) and limited it.
Tho I think Mihawk and Akainu can do similar stuff as Roger/WB in the way of fighting Kaido and hurting him severely.