I brought this up a couple months ago when it was mentioned but I never got much of a response from it. In 2.4, the combat log is getting a huge overhaul. From what I understand, each parse-able line in the combat log will now be unique to unit GUIDs. Basically every unit will have its own unique GUID. So, lets say you are fighting two mobs, each of them are lvl 70 and both are "Ogre Warlock"'s. Basically, from what I understand, the new combat log will be able to tell the difference between the two mobs.
So what I'm wondering, is Recount, Threat, and any other damage or healing tracking addons being worked on to take this into account? With these great changes, Threat, for example, will be able to accurately track threat against multiple targets w/ the same name. Pretty handy!
Current 2.4 Recount does not use GUIDs to distinguish NPCs. For a Threat-meter it is a no-brainer because threat per mob very much matters even if they are named the same.
For a damage meter there is a very real question here: Does this make a lot of sense? So far my answer is mostly no. With very few exceptions non-uniquely named mobs are "trash". And typically over the course of a damage meter collection session (say a raid) you'll kill a good number of them and most people actually never even worry about them.
Even if you handled NPCs on a GUID basis, you'd want to have at least the options to merge equal-named trash into one lump, because they may otherwise clutter your display with what is otherwise not all that interesting data. A lot of people I think do actually use damage meters to look at raid members only, with the possible exception of raid bosses, but these are all uniquely named leave pets and guardians.
GUIDs will help distingish pets easily when we have the announced UnitGUID() available.