Kleps had a post a while back on segregating the playbase. Basically, the idea is that groups are happiest when all the group members share the same goals and are roughly the same skill level.
I think there is some sense to that when you look at LFD groups. Levelling instances are pretty much on the same page, as are normal 85 instances. It's really only Heroics where a lot of the negativity and conflicts come into play.
This is because there are three separate groups running Heroics: people gearing up; non-raiders collecting Valor; and raiders supplementing the Valor gained from raiding. Yet the goals, methods, and standards of these three groups often conflict. People start complaining when the tank is new, or refuse to use CC, or skip bosses trying to get to the end as fast as possible.
But suppose that Heroic 5-mans never gave out Valor? That the only way you could get Valor is from raiding. What would happen?
Well, immediately, Heroics would become the province of those people who needed Justice points and Heroic blue gear. People who had "outgrown" heroics would not run them. Heroic groups would share the same purpose. People would not skip bosses. Tanks learning the ropes, or being less-geared, would be more understandable. CC would still be used, as it would be less likely that everyone would out-gear the instance.
A lot of other people have said that having Heroics give badges (the old equivalent of Valor), was the worst mistake made in the endgame. There is some truth to that. But it was done for a reason. It was done because people who did not raid 25-mans had no way of advancing their character. But in the current game, there are 10-man raids, 25-man raids, as well as normal and heroic versions. Pick-up groups are a lot more common.
Additionally, even with just Justice points a non-raider would still be able to advance her character. When new tier of raid gear comes out, the old tier rolls over to Justice points. Admittedly, the non-raider is behind the raider, but she can still advance and make her character more powerful as time passes. It isn't like Vanilla, where if you couldn't raid, that was it for you.
There are advantages for the raiders as well. They are freed of the necessity to run instances long after they have outgrown them.
The big question is if this will increase queue times. After all, forcing raiders into the Heroic LFD pool makes the pool larger, and more likely that groups will form. Now increased queue times are certainly possible. But consider that leveling groups and normal 85 groups still form with reasonable queue times. Those pools are not artificially inflated, and yet you can still get groups for those dungeons.
Badges of Justice dropping in Heroics was a necessary solution back in TBC. But in Cataclysm the options for endgame, and for advancing your character, are much wider. Valor points in Heroics are no longer necessary. The Heroic experience will be much better without them, when all participants are on the same page and share the same goals.