Karma to me is a matter of cause and effect (how do we respond to what's happening) not a matter of superstitious justice (that something is happening because of such and such).
So while I might get a sense of poetic justice that someone seems to have "gotten what was coming them" I don't consider that karma.
Nor is my compassion controlled by my sense of poetic justice, though I may have other principles overriding my interferences.
For instance, I might see someone suffering and I might initiate action to reduce their suffering. Someone is so hungry that they are sickly, so maybe I give them my lunch. But also I might see someone else suffering and conclude, still with as much compassion, that they need to get out of that situation on their own or they'll just wind up in it again, maybe I'll keep my lunch but give that hungry person a few dollars and let him work out the budgeting issues for himself.
I always feel badly for people when bad things happen to them, but that doesn't mean that when it happens to a douchebag that it might not give me a little smirk. That is not a reduction of empathy. It's an addition of humor.