There are some fundamental problems concerning the balance from the basis of the instance of rofl. It is a bad basis to try and balance around as damage and survivability can heavily vary between players due to differing styles of tanking/supporting, as well as the randomness within bosses and trash themselves.
a) Damage will vary depending on content.
Boss 1: Area of Effect classes are incredibly favourable to it, falsifying the actual damage dealt between bosskillers and trashers.
Boss 2: Circle randomness can easily skew the recorded damage into either direction
Boss 3: You go in and you deal damage. Otherwise it's 0.
Boss 4: Not really random, more tab-luck.
Boss 5: Depending on events and who gets them, damage can be really random.
Trash: Depending on the confidence and ability of tanks, classes may feel very strong or useless.
b) Playstyle is everything.
If you have a tank that just steadily runs and pulls one mob by another, killing most of the monsters while being on the run, classes like scouts and champions have the upper hand in dealing damage, simply due to their damage being consistant and less burst based on monsters. If your tank likes to group up enemies because they can handle the heat and make sure their party doesn't die (as in, having enough crowd control in party to protect everyone), classes like the mage or warden will excel due to their high burst aoe type damage.
c) Supports are far more important than given credit.
We all know the warlock, but did you know that you can get an additional 17% multiplicative and another 24.5% multiplicative damage by just having a S/P and a Ch/D in your party? Depending on your supports though, burst classes may be favoured or DPS classes may be on top.
d) Damage isn't everything.
Especially when you come into the very high end of ROFL where most of your party has their golden gear and seeks to complete the instance for mostly income, Utility becomes much more of a factor in farming the instance consistant than damage. If you can prevent a wipe with a clutch cyclone you just saved yourself and the party 3-5 minutes, contributing to efficiency much more than another, higher DPS class would.
Conclusion:
Player gathered data that does not take the difference of tanks, supports and randomness into account is factually useless in determining balance between classes. What may seem overpowered in one group may just suck hard in others. The variance is so big that there is no conclusive evidence to be gathered from posting random scrutinizers without proper context.
The team does a fantastic job in balancing and their efforts are often overlooked within the community. Generally speaking, the availability between classes and the feeling that you can be useful with practically any class is remarkable. Yes, statistical outliers happen, but generally speaking, they are few and far in between.