There was a discussion on one of the forums I frequent this week about the relative merits of DPS and Total Damage. I say discussion, as there was the usual degree of name calling about which was most relevant. In fact, as someone who spends all day crunching numbers I can happily say both are, and neither are.
(Sorry for the egg-sucking lesson for those who do understand basic stats, but for those who don't ...:)
DPS is a measure of damage over time. The more damage you do in a given period of time, the higher your DPS score. However, this can be skewed - a mage who does a single 10k hit on a mob with an instant cast and who is then splatted may appear to have a high DPS rating (depending on how you calculate the time element of the DPS stat), but in fact they made only a minor contribution to the fight.
Total Damage is an open-ended stat that does what it says on the tin - it adds up all the damage inflicted during the fight/raid/whatever. However, the significance of that varies a lot - a 3 hour raid will naturally have a higher total damage than a 90 minute one (and the same with a 10 minute fight vs a 2 minute one) .. you'd hope at least.
In reality, you want to look at both - high DPS and high total damage = result. High DPS but low total damage, or low dps but high total damage are going to be less helpful in a raid (the former is dependant on how long there was active contribution to the fight, the latter on the need to down in a fixed period, e.g. enrage timers) and a low-low result is pretty obviously a bad thing.
Of course, when deciding on who to involve in your Emalon pug you can't really look at exhaustive raid stats and, assuming they're not a complete muppet who'll die to the first rockfall, DPS is probably going to be close enough (so, horseshoes, handgrenades and pug-forming) but if you're looking at your own performance over time, or your associates, you need to look at a broader range of stats, for which I'd heartily recommend Wow Web Stats (though there are other alternatives I've not investigated at yet).