It looks like he took two Laser Matrix between his head and his shoulders, which isnt ideal. Also i noticed hes running Auspicious Spirits and he has the crit to make it work, but his spirits are only 4% of his damage. They should account for a much larger portion of his damage otherwise he needs to just be running shadow word death.
Doom's Hatred is a really bad trinket for us too
Ah ok i think i see what the problem is. His void bolt casts are insanely low, probably half of what they should be. I put up a 95 parse last night on H Taloc with void bolt being my #1 attack for the fight with 46 casts, he only cast it 22 times. It looks like he isnt using it on cooldown which is rule number 1 for shadow priests. His Shadow Word Void casts are also pretty low, as are his mind flay channels.
EDIT: if i had to guess, he is probably waiting for his mind flay channels to fully finish before using void bolt, which is a no-no. He needs to interrupt whatever he is doing (mind flay channel or shadow word void are the only two abilities that should be competing for that global) and get that bolt off even if it means clipping the channel early