Need to use an SLT, Darkness, Rallying cry, Salvation, Barrier, (possibly a devo aura)and as many Damage Reductions and health pots as possible, stagger thru the rooms over 3 seconds, not all at once, SLT is good, but not godly (paladins should save their bubble til the 2nd transition as more people are going thru at this time)
MOTHER Cheese strat for mythic [The Last Watch] Frostmourne