I use a barbarian a paladin 2 ciphers a priest and a mage (although thinking of dropping the mage)
Formation doesnt matter much other than casters near the back.
My opening moves are priest uses interdiction barbarian uses shout. If its a really messy fight my ciphers will use item summons if not they will position themsleves to flank the main body to attack mages etc. Paladin uses an item bound spell - those rot gloves are awesome (my paladin is a glorified mage with an aura when loaded up with items that have casts per rest) mage casts depending on the situation maybe a slicken, if a messy pull he will use Kalakoths minor blights.
At this point most things are dazed weakened frightened and possibly sickened.
Engagment
Both ciphers will find an appropriate target to body bind (either a mage/cleric or the bulk of the enemies) this diables pretty much the entire enemy party with stuck /paralyze (the aforementioned debuffs wrecks enemies will defence, so now you wreck their deflection and immobilize). Barbarian who is not a tank uses fury and attacks the main group, paladin also attacks or casts another spell, cleric may use holy radiance for accuracy buff if a small engagement, blessing if a larger one. Mage casts whatever fits the situation - I do like blinds.
Attack horde, reapply body binds as appropriate and one cipher may use phantom foes, use flames of devotion for heals etc.
Long sotry short Ciphers are over powered body bind is broken and when you stack damage on them: biting whip, two handed, savage attack - estocs: they break the game. (most things in game have low will defence; the main exception would be spirits)
This set up works fine on path of the damned, although admittedly I haven't finished the game yet, but Iv'e yet to encounter much trouble aside from early game shadows and phantoms.