They just need to make better anima power for the classes that need help. The reason I do well on ret is because the powers that we get throughout the tower helps us tremendously as we get higher. By the time I hit the boss I am usually doing at least over 50% more dmg to them, and at most over 100% dmg to them, usually kill bosses in less than 30s.
But that because the anima powers are tuned really well for some classes and terrible for others.