Probably been reported already, but here goes.
The 4k Item Level Weapon/Armor Enchant gives an 8% damage increase, damage increase depending on which is chosen, and base damage increase as well from improved item level.
But with no combined rating, all classes lose 20% offense and 20% defensive stats (4k IL x 5 offensive and defensive stats). The damage gained from the enchantments do not offset the damage lost from loss of ratings in addition to the loss of survivability. This same concept probably holds true for healers and tanks.
Is this intended or not intended or is the observation incorrect?
Possible fixes. Add combined ratings to weapon/armor enchants or increase the output of said enchantments.