Just keep an eye on the submerge timer as he can be fairly trollish with his times, if he submerges and has dread thrash up and is about to cast naked and afraid
He will use the thrash then instantly naked and afraid so you need to be ready for your OT/'s to take the dread thrash
Outside of that you can just have shield block up + demo shout for every single one and rotate shield wall and last stand, ideally combining the last stand with a shield block + barrier due to it not having the damage reduction component
Ideally you need to practice and consistently be making it to phase 2 with no deaths as random deaths are pretty likely in p2
Sha of Fear helper addon helps loads for the DPS and healers, less so for tanks as sometimes you just need to eat the spray if you get bad RNG on where the orbs land and just run around troll spamming barrier