Im running a balanced group with a chloromancer/archon and cleric. This brings very effective tank and party healing along with tons tons of buffs. i bring another elementalist/Stormcaller mage that brings a spell power buff to the party that stacks with the chloro/archon buffs and then a ranger/marks/assasin. if i had it to do all over again as nice as the ranger is to dps the ele/stormcaller mage puts out an easier rotation and better numbers then the rogue.

For buffs to stack or not stack any hour long buff that increases a stat doesnt stack with any other hour long buff that increases the same stat. an archon can provide all the buffs shy of an endurance and speed buff but they have one that increases dext/wis/str/int which you would have to have 2 bards to cover those stackable buffs. If your wanting a good synergy i would do warrior/cleric/mage(chloro/archon)/mage dps x 2.