The only problem with Pharos Sirius is people trying to zerg through it.
First boss, concentrate on taking down adds, and if you have stacks, let them dissipate before dpsing boss further...
Second boss, leave the eggs alone or only kill one egg when it lights up (speckled egg preferred I believe)...
Third boss, might as well be considered trash as it's too easy...
Siren, silence lunatic voice and prevent the crawling mobs from stunning people... And don't be afraid to use healer LB if things look bad...