Originally Posted by
Nymie
Since you are not a shadowpriest (I assume) to expand on what was said earlier, ToF (Twist of Fate) is a great choice for this fight. Once you damage something below 20% health there is a 15% dmg (or healing) gain for the next few moments. With so many adds in that fight, it is a huge boost to dps. So once your priest understands when to use this he or she can really bump their numbers. They can Shadow Word Death adds when the add is below 20% and receive the buff and then use it on the boss (macros work nicely on this).
Cascade does not have range requirements that Halo has so the priest does not have to spend time positioning, and it just simply produces better numbers during Elegon. I am assuming this is normal Elegon so the priest should also utilize the dmg buff that occurs when standing on the platform to mind seer the hoard of adds once the tank has picked them up no matter the positioning.
If the priest isn't potting he/she is doing it wrong.
Their gear is fine (hit capped, reforged okay though not going to sim them to make sure). Shadow does amazing numbers this fight so I really think its roe talent/player needing changes. Good luck in your raids!