One thing I'd probably recommend if you're running 4 disc with a proper tank charly, is to only have each priest shield themselves I did a similar thing running 4 ret + 1 prot w/ kings and it really turns out that the tank doesn't need the shields, it was the rets that had survivability issues due to all of the group damage spikes. Now I just have them all kings themselves and it goes much smoother. Given all the atonements on your tank he'd be pretty much invincible outside of one-shot mythic+ mechanics.