unlike Fallout 3, Karma has almost no use. I played this game for about 150 hours so far and only time I needed Karma was

Is there any other way Karma plays its role like fallout 3?

None, it's redundant.
Not use for it at all anymore really.
Fallout is suppose to be gray in morality.
A karma meter does not help that exactly.

IMO, remove it by FO4, no use for it anymore anyway.

One of the ending slides is linked to your karmic status. That and the thing you mentioned are the only thing that karma influences I think.

I find it a bit silly that it's so hard to be bad in NV. No matter how many conundrums you solve in a morally grey/black fashion, you'll shoot right up to being a saint after offing a few ghouls or fiends.

The karma system is wonk in New Vegas and only used in a few of the ending slides and to keep Cass around.
The reputation system replaces it completely in functionality and the karma system could have been ditched.

Wiki can put it better then I can http://fallout.wikia.com/wiki/Karma

Not many two dialogue topics, including the one you posted, and the epilogues.

However I'd like to see it back, just a whole lot better and more thought and consequences to go into it.