Where's the silence spell or other enemy debuffs to neutrilize the PC casters? Granted not all our spells have a verbal compenent, but a good deal do. Give high level divine spell to cure it, but no potions, and you help promote more of a melee/caster balance.
give epic archers silencing arrows (on critical hits maybe?) in addition to the enemy caster spell list.
it'll make soloing on a blue bar a little harder (or longer rather with only having some options limited), but in the group dynamic, it'll give people in other roles more of a chance to actually participate if the caster is occasionally cc'd (altho still able to function, just at a reduced capacity)