Mob damage has gone low. Help!

Hey,

I'm currently writing a plugin similar to HeroicDeath.
However, I'm using the onEntityDamage event and now,
without me modifying the damage in any way or actually cancelling the event,
it now takes more that 3 creepers exploding right beside me to even half kill me,
and more than half of a skeleton's arrows bounce of off me.

Did anyone ever experience anything like this before?

-Kierrow