I have seen exactly what you describe. A few years ago I noticed one bartender busting butt while the other was semi-rude and did as little as possible. I ask if they split tips and was told they did. I gave the person the some cash and ask that they pocket it and if it was a problem I would speak to the bar manager. I did not want anything going into the pocket of the lazy prick this person was stuck on shift with.
Bravo Poppaj! (never thought I would say that to you, right?, haha)
Had a similar story. I was at the "new' Waffle House on West end of PCB. Sat down, time went by, no one took my order. I notice one waitress girl, her name is Trixie, was basically running the restaurant herself. A hustler. She kept looking over at me and finally just walked over, cheerful, took my order. And then she brought me my order within 5 minutes. All good. An obese slacker chick came over after my food came out and asked if I needed anything, etc. "no, i'm fine". When I checked out, Trixie checked me out. I asked her if she was supposed to be my server, she sheepishly said no. I asked her is she would get the tip. She said no. I said OK, no problem. I tipped $1 on a $12 ticket, and gave Trixie $6 cash. Eazy peezy. I told Trixie that I know what goes on in restaurants, and encouraged her to apply at any of the top restaurants on 30A; that she was that good. I then wrote a good review online and mentioned Trixie (reviews and mentioning names in online reviews is a HUGE deal in restaurants). I believe that above and beyond service should be rewarded with good tip, online review, and telling the owner/manager.