The recovery speed was faster than the rate of injury, which was exactly why the Human Emperor's Immortal body was a vexing issue for those Deities. Possessing both the effects of immortality and an extremely strong recovery ability, it's no wonder that even those more powerful than Zhou Tian found themselves without any method to defeat him when facing such a combination of abilities.
Now, though, with his recovery ability greatly weakened, the Human Emperor's Immortal body was still a very strong ability. But, if one were to evaluate it, both in terms of value and threat level, it was inevitably greatly diminished at that time, and what could almost allow Zhou Tian to fight above his level had begun to turn into merely a life-saving ability. At least when facing opponents too much stronger than him, Zhou Tian could no longer rely on the Human Emperor's Immortal body to ensure his ultimate victory.