My guild luckily has two Ret Pallies with Divine Sacrifice and 2/2 Divine Guardian for this encounter in the 10 man version. We had the ret pallies rotate using Divine Sacrifice and Hand of Sacrifice to help mitigate the damage of Plasma Blast in Phase 1. Divine Sacrifice also provided use in Phases 2 and 4.
(The Paladins did bubble when they used these tactics.)
Edit: This is for a single tank strategy.