if i am casting with a dmg charm in a cata on my mage, does mpk and mpa work in the cata or does it just work in the arena?

arena only

not true, MPA works, mpk doesnt

I believe that both of them have a chance of working.

I know that xx per attack has a chance, not entirely sure about xx per kill though

this

They only work when attacking EPs or higher (shamans, etc.)

they are only effective in arena, they have a small chance to work on cata

I know for a fact that this is not true. They have a % chance to work on any mob, it just works better on EPs and shamans because you have to hit them more.