I must have forgotten the part with Boa, I was thinking there was an action scene showing it. I would say Garp is likely to have and if Dragon has it then there's no real reason Garp shouldn't. Sengoku as Fleet Admiral should also have it since many pirates seem to have it, the Fleet Admiral should always have it I would say, it should be a pre-requisite for FA.
As for WB this is part of the problem for me about the earlier portrayals of haki, before the blackening was shown(and with Sentomaru) there is shown a haki that doesn't require the skin changing colors. Also WB hit Akainu at MF which most everyone says is proof WB had Armament Haki(I'm not disagreeing) and there was no coloring to showcase it in those chapters. So I take that information(invisible haki) and say maybe BB used Armament Haki in ID to hurt Luffy and not exactly his DF nullifying Luffy's power yet people say impossible.