If you're worried about threat handling then yes you're tank should only be the one to have Righteous Fury. You're shockadins should focus on Holy and Ret Tree to have more damage.

In terms of Boosting low level, the build itself can run you're low level toons wearing Shield, Weapon, Back, Trinkets, Rings and Necklace only. This will save you a lot of repair bills. I run SFK, SM Cath, Ulda on 1 pull and Strat Ghouls Area on 2 pulls since there's a gate in between them

In terms of Heroics, for 5 paladin team, if your tank will be using Holy Shock both offensive and defensive often then you'll have a problem with Mana since you're wearing tank equips and you'll only be pulling 1-4 mobs at a time. The Mana that you're getting from Blessing of Sanctuary are not enough to sustain you from spamming Holy Shock, Consecretion and other offensive skills. In heroics, most of the time Holy Shock and Lay Of Hands are like my OHSHIT button for my tank if the healer can't keep up healing or to my Slaves if the mob jump into them and healing them which also generate threat back to your tank.

With 5 Paladin setup I would have 2 Paladins with Beacon of Light since paladin's are not that good in AOE healing.