The character's personality has to be taken into consideration. We can all take powers sets and put them against the each other. If Wolverine wasn't as tough, and very strong willed of a person as he is, the HF may not have as big of an impact as it does i.e. Wolverine wouldn't take as many risks, knowing the amount of pain he's about to receive or build up an resistance to pain over time because he's too scared to feel pain. But this isn't the case. And like Wolverine said in Wolverine vol. 2 issue 31, "it's not his style" to run from any situation no matter how taxed his HF is.
To me it's a combination of the Adamantium, HF, and at the core, toughness and will-power. That's why it's so hard to KO Logan with one hit. And there are too many examples of him taking several hits from Hulk and other super-powered beings.
You need to overload Wolverine' HF in order to put him down and most of the time it takes a group of foes to do it. Hard for one opponent to achieve, but not impossible.