Another minor point worth mentioning...
Let's say you consider House an evil karma character simply based on his selfish intentions. Yes, luckily his selfishness DOES lead to feel good being done (
EDIT: lawl, <----pro typo showing off my two languages, "viel gut" in my mind comes out as "feel good," lolololol. Meant to write "a lot of good"), but perhaps you're more focused on the intent of a person than the outcome.
In a similar scenario, if say, a thief were to shoot a corrupt cop who extorts the people of a small town community because the thief knew the cop was the sole witness to his crime, but the death of the cop is a relief to many and the town as a whole is better for his death, does the thief gain good karma or evil karma? On one hand his intentions are bad, on the other, the outcome is good. With Mr. House it's similar, but instead his intentions aren't SO bad; fending only for yourself, in my experience with Fallout, is referred to as neutral karma, as it's only natural to fend for yourself and you can't EXPECT someone to always do the right thing at all times and care for everyone and everything.
In that case, let's say Mr. House is neutral karma. Well, two kinds of people will reward you bad karma for killing them: good karma people, because you've killed a good, helpful person, and neutral karma people, because they're, as a whole, innocent.
If you look at it that way, I think it's quite natural that killing House gets you bad karma.
EDIT: Though just on a side note, I studied law for a time and I can tell you that under German law at least, your general way of thinking is correct. As in, a person who does something good though they actually do it because of bad, criminal intentions, and those intentions can somehow be proven (which realistically never happens of course
) then they're still treated as a criminal. If I want to murder somebody an accidently shoot some guy that was about to murder the exact same person I wanted to murder, I'm still guilty of attempted murder. (infact you can have a debate about if I'm guilty of successful murder (negligent or not), since I DID kill somebody in the end and the argument of "I did it to protect the other guy" clearly doesn't apply to me)
With House it's a tad bit different since he hasn't commited criminal acts, but rather only commited GOOD acts for all the wrong reasons. The law, in that sense, doesn't OFFICIALLY support your argument, but rather in
my opinion, the general philosophy and ideals of German law match your own.