Since the latest patch and the changes to XP, the XPM stat has become increasingly less useful or reliable due to the huge amounts of bonus XP that players can receive in moments of the match. It used to be one of the stats which was most resistant to game events, so that if, say, a player had 500+ XPM at the end of the match, you could judge that that player had done fairly well to keep pace with the game and were always in and amongst the action and/or farming efficiently.

Now it doesn't really work out like that. A team that is losing the game, and may indeed lose the game in the end result, can still finish with multiple heroes with really high XPM, even though throughout the game they never realistically achieved that level of constant XP gain. I've seen base defenses where the team that is clearly winning loses a few heroes (who may or may not buyback and push to victory), and the heroes getting the kills suddenly go from a poor XPM score to something like 500 or 600 XPM. This makes the stat rather useless for judging anything.

Additionally a lot of the time both teams will end the match with a majority of heroes on 400-500 XPM despite it just being a standard game of Dota where there was one team with an advantage, with properly farmed heroes, who pushed their advantage to victory (the opponents did not farm or fight as efficiently, and would previously have poor XPMs in the ~300-400 range at best).

My personal interest in this is less about the scoreboard at the end, and more how this relates to tracking personal stats. Tracking my XPM versus my team (other players average), or versus the enemy, or versus the match average, was a very useful exercise in both judging the type of match and my own performance in the match - and my improvement (or lack of it) per hero. Now that stat is just too unreliable.

I would suggest for these reasons that there needs to be some separation of the 'classic' XPM stat, consisting of XP from creeps, roshan, and standard kill XP, and the XP returned as bonuses when the bonus XP is over a certain threshhold, since these amounts of XP warp the statistic.