I suggest that mobs have a health indicator above their heads that shows how much health they have left. 

Well, its mostly a health bar.

Thanks for the suggestion! I'll look into adding this after we've updated to 1.8.

Mob health bars have been added.

Yay

The health bars are cool and all. But, they only stick around for a second. Can you make them stay there longer? Perhaps staying there as long as the player is looking at the mob?

The bar should stick around for 5 seconds after you've hit the mob, but it's only visible if you look directly at it (which appears to be a bug with the plugin).

The mob moves around, hard to keep the cross on the mob. Can you fix it so that we can view it even without having the cross on the mob?

I'm focusing on the FNAF minigame right now, but I will be on the lookout for an update for the plugin.