There was no official statement or story that his HF got slower. Besides, he has recently took a nuke, fell from the atmosphere, healed in seconds after being cut to tiny pieces etc etc. I already mentioned that Way (the guy who writes the main series tends to downplay his HF for the sake of plot) but not nearly as bad as it was in the MK issues.
In that issue he on purpose kept his leg from regenerating, if anything, him losing counciousnes after having his leg chopped off was written for the sake of humour (him playing "pirates of the caribbean"😉 and may not be PIS but is definitely a very low showing that controdicts 95% of character's history. While him requiring medical attention is just a whole new level of that. In comparison that'd be like Flash getting tagged by a turtle.