From the Busoshoku Haki wiki:
I think you are wrong in saying that they weren't affected. They clearly were affected as you can see from the wound on Sakazuki's shoulder. Since both questions have a different answer, I'll reply one by one.
Whitebeard vs Kuzan
He then got stabbed by Whitebeard's bisento, to which pirates are seen wondering if Aokiji was stabbed with Haki and if he was dead. Aokiji told them not to spout nonsense before grabbing the bisento and using his Ice Block Partisan attack. All of a sudden, Jozu attacks him and Aokiji is caught off-guard, even bleeding from his mouth.
As you can see, Aokiji was not hit by the Partisan, which was most likely imbued by Haki. This is, because he opened up a hole, where the partisan would have hit, just before it would hit. If he hadn't he probably would have been stabbed to the heart. Marine admirals use their power smart and efficiently, but it doesn't mean they can't be harmed. This can be seen just a moment after, when Jozu attacked him with his diamond arm and he was seen bleeding from his mouth.
Marco and Vista vs Sakazuki
Apparently, Akainu has found some way to avoid Haki attacks, as he was not visibly harmed even after Marco and Vista sliced him in the neck with Haki infused attacks. It is unknown how he can protect himself from Haki-imbued attacks but when he was attacked by Whitebeard with this type of Haki, he could not protect himself and he bled.
With this one, I can't rely on the wiki as reference. My opinion would be that you shouldn't forget that these people are human also. They can train their bodies as the others can. That said, and I don't really want to start a discussion on who is stronger, but to me it looks like Sakazuki was hit and he might end up with a scar from that attack, but that it wasn't enough to phase him too much more than that. He probably felt some pain from it, but nothing more than he could handle. I'm not completely sure on how Logia exactly works, but he might even be able to patch up his chest and shoulder.
Like Kuzan did, after he lost his leg. Replacing it with an ice leg.