Compared to the other predators, I see absolutely no reason to have the lion be class 9. Lions weigh around 400-500 pounds.
The minimum I could find was from Zimbabwe, where the minimum is 4300 Joules or 7mm in diameter.
Other countries in Africa make the 375 the minimum. As well, lion hunters consider the 365 as the best rifle to use with the 416 being the absolute maximum.
Thus, with the Zimbabwe requirements in mind, I think that lions should be put in class 7 with the bears. This makes sense given the weight of the animal and what's actually used for lion hunting irl.
I'd also put the mule deer in class 4 with the whitetail as they weigh about the same.