I know, as with all of my personal ideas, that opposition to this from you readers will likely be strong. I can just hear you saying now: "We can already do this!" Yes, mods like DamageMeters can track damage and healing done, in an instance or out, and across the group or otherwise. But they can't track killing blows and other stats, and not every player has access to the info-- it would benefit from being done by Blizzard (we already know they can do it in the battlegrounds, instances would be no different), and it would give us a standard system to track these kinds of stats for those of us who are interested.
The other objection, I'm sure, will be that some players don't want to know this info. Guilds will sometimes ban DamageMeters output in the chat channels, because they want their raiders to be working for a win, not for individual DPS. But to those objections, I say that if that was a problem, we'd already be dealing with it. If anyone is going to work for individual DPS, what's to stop them from installing DamageMeters and doing it right now? And if someone is working for themselves instead of for the raid, the simple solution is to just not bring them along to the raid. If a meter makes them ignore helping others, who needs them?
Of course, the other objection you might have to this one is that Blizzard should be working on more important things, and on that I can't really argue. But Blizzard, if you're listening and have the time to do it, I'd like to see the numbers on what my party is doing in instances.