I'm xbox 360 unfortunately. It's crazy how difficult it is, with me having a Lvl 28 warlock my parter having a Lvl 27 Titan and a friend of mine being a Lvl 28 hunter is ludicrous!

Can't remember what the knights shield is, think its arc? Anyway get yourself an elemental fusion rifle for the knights. I had vision of confluence (scout rifle with solar) so the wizards were easy. Guess your stuck unlocking the door with the 3 waves? I got stuck there for a while. Hang out in the hallway and attack from there. If you make it to phogoth, try not to get stuck in the opening room, it's a pain to get out of with all those shielded enemies, and the shrieker sucks. There's a rock in the far left corner of the arena that you can crouch and avoid most damage from. (Dont go to lowest platform, you've gone too far) Have someone post there religiously as a spawning anchor, since it's timed respawns. Biggest issue is the knights. Good luck.