In terms of balance, I think it is important to note that there are several villains that make the heroes damage themselves. Depending on your team, Legacy's Galvanize can end up hurting as much as it helps.
Just a word of caution : the total win rates of heroes in our statistics may not be comparable. We don't have enough games , yet, to make the hypothesis that each hero fought approximatelly each villain on each mode the same number of time - or at least in a statistically unbiased way.
We may have a bias, here : did Legacy, Wraith and Expat fight the same villains on the same modes ? Legacy is often used in demo and "learning" games, while Expat or Fixer, etc, are often kept for later, when you are more experienced and try "bigger" villains. It may create a bias. We also have to compare at least the size of the team he is in with the other's team - especially because he is very good with many heroes by its side.
I plan on doing statistical analysis on hero/villain pairs to know what results are relevant/statically valid "some day", but for now we can't "prove" much.
Also : heroes have different complexities. Legacy is "easy" to play, while the other heroes get more powerful with player experience. We may see an evolution of the stats as the players become more experienced (especially if they don't change their mode of play) and we accumulate more games.
In my opinion, Legacy is good, but not better than the other - he is just easier to "grasp" and play, easier to "grok", as they say. I would say he is the easiest hero to grasp, in fact - the "difficulty zero" hero of the set 
However, the fact that his basic power makes everyone more dangerous to the villain give a better chance to his team, whoever they are, from the very start, even with no other cards in play - it IS a big advantage.
Another factor in the analysis that is impossible to work through is the player. Not all players are going to play a specific hero the same way. Many of us have specific attitudes and approaches, some of which are going to be less optimal/effective than others. This is something that can't really be included in the analysis.
Just something to think about. It might already have been discussed - I honestly haven't been tracking the analysis, primarily for reasons like this. 
SoundofTrees, I really don't think Legacy is a difficulty zero. As a support hero you make the best plays when you know the other heroes' decks hands and abilities. I wouldn't move him to a two, but playing Legacy is not always easy. I would argue that Ra is easier to grasp. Playing Ra can sometimes feel like asking yourself "Should I do lots of damage or should I do a lot damage?"
Thats part of the reason we need so many data entries rabit - The more information we have haave from more sources, it will reduce the amount of 'player error' or 'player style' bias - youll notice even the most rabbid contributers to the stats only have about 8% of the games - and only if they played /every single one of their entries/ with the same hero would it have a noticable effect. Since no one is doing that, its not that big of a deal
and as we get more and more entries, those 'total contributed' drops farther and farther, so even the top guys arent swinging the stats to far in one direction or another. Over time and enough data, such variances smooth out into the true averages.
Now why the stats project isnt perfect, and will never be able to tell us /exact/ information - there are simply FAR to many permutations to ever get all of them and then /show/ all of them - it can at least give us general ides - So while the 'Individual hero' and 'individual villain' pages are fun - most of the information we're going to be getting out of this project is 'Who wins the most' - 'who is the hardest/easiest villain/environemnt'
i /could/ set up a data collection for how each hero plays with others, but man the data involved with the number of permutations there on just 1 hero with another… my god. I weap just thinking about it.
Totally understand, lynkfox! My wording was poor, and I didn't realize it until I read your response. I am not saying I don't think there's value in the analysis. I know the >G folks are very interested in seeing the results, and that's reason enough for me. 
But I also understand the statistical possibilities and how it works. I also shouldn't have said "primarily", as that's not true - I'm primarily not getting involved because I just haven't been able to make time to document all the games and then get them into the data.
I'm very glad you guys are doing it! 
True, Legacy becomes better with experience. But when you begin to play, as most of his cards have indirect effect by boosting/protecting the team, you can play nearly anything and have everyone else become more effective. You can have big effects on the game without even knowing why 
"dificulty Zero" is an exageration, of course - but he probably is the hero that feels the more effective as support, even if you don't know what you're doing.
I also don't think Legacy is a difficulty one character. Considering his utility for the team as a whole and ability to easily explain the structure of a hero turn to newbies, I would reclassify him as a difficulty fun character.