I'm 100% against meters like this being in the game. To boost your own personal abilities, all they need to do is make the Character Screen give you ACCURATE information. This was a major problem in Diablo 2 as all of you know.
The reason damage meters are in games like WoW is because they have different needs (none of which exist in the Diablo environment). For example, certain raid / dungeon encounters are DPS races - where if you DON'T kill something fast enough - everyone dies. If you're not carrying your weight, there is a real consequence. Diablo (as far as we know) does not have encounters like this. And TBH I highly doubt we'll see anything like that in Diablo.
As was mentioned though, dps meters had some negative effects as well. You couldn't even go through low level dungeons anymore without some elitist spamming the meters to show off that his twink is doing more damage than normal players. The next thing you know - everything is compared to high-end instead of normal. A fight that really only needed 5k dps, became a 10k dps minimum.
Quite frankly, crap like that only appeals to elitists who have nothing better to do. It's a game, play it for fun. If people are wearing gear they find, and using abilities they put points into, they're going to be able to kill things and carry their weight. But if you have a damage meter, you're going to be butt-hurt over the fact that they're only doing half as much damage as you, who is well geared and knows exactly how to play. So you'll kick them thinking they suck. Go make some friends, turn them into elitists, and then make a private game so you don't have to kick every casual player who enters it. This really isn't even worth arguing, stupid idea is stupid.