party wide it depend on what class my inquisitor is and of his/her specialisation..
but i always take iron bull speced with pommel strike, basic guard n aggro ability, some 1h passive and the rest into his reaver tree. then if i'm on nightmare i always take 1 mage, usualy i take vivienne if i'm something else than a rift mage, if i am a rift mage, i'll take dorian and his walking bomb sheningan, plus all mine for some explosive combination. of course i put more point in spirit 1st as his main job would be to barrier me up for increased fire mine damage n make sure i survive through nightmare lol... also, if i go with vivienne i usually go winter tree up to ice armor, with ugraded ice mine, but only if i'm not a mage that is... if i am a mage and that i bring vivienne along, i spe her more to distribute shock all aroun the place so my spell are more powerfull..
then again if i'm playing a class which can litterally spam a lot of high dmg spell or talent, i'll use cole and will manually setup a mark of death and trigger it myself.
if not i'll just use serah to pile up even more dmg.... thats usually how i like em =)
btw rift mage is pretty serious even with the immune weakness bug on immune to sleep ennemies lol... just defeated a high dragon (the one in the hissing haste) in like 5min with staff of corruption the staff was electricity, and i used a lot of electric spell....maybe missed a bit of mana regen but i gain in damage in the debuff fro shock n all those sweets spells in storm tree ^^ but that another topic....
i am merely a perfectionnist, and i also love big dmg =)