This is a cool idea. That said, given you have an Ascendant that could restore the Paladin's resources with the Cipher spell that gives Brilliant, maybe going fully Pally to get Divine Retribution isn't needed? In fact, if Chill Fog is going to be a key element of play, you could also consider Steel Garotte / Tactician, which should be able to self-generate Brilliant if the Chill Fogs nail all the enemies and flank them all, right? Or if you flank them all with other Cipher spells like Phantom Foes?
Or SG/* where *class brings a bit more to the table for tanking or damage, if the cipher (Ascendant) is still restoring reources on the Pally/* with the cipher spell that gives Brilliant? Maybe even SG/BloodMage or SG/Evoker? or SG/Streetfighter or SG/Trickster (for tanky)?
If you go this route per Boeroer, maybe get the gear that gives bonuses on downed allies ... i forget their names, but there are 1-2 late game? Presuming the downed summons count.
The key to duoing or soloing the bosses/megabosses generally is replenishing your resources, so having the Cipher as one of the 2 toons is probably a key element (not 100% necessary -- see recent single-class monk discussions -- but certainly will make things easier).
You could also flip it around and equip chilling grave on the pally, that way all the front line enemies would have chill fog on them. You would lose the focus gain though.