Only one person is needed to pull levers on each side in the north part, just need to be quick. The animation for pulling a lever is much longer than getting it pulled actually is. It keeps going for some time after the lever has been activated. The trick is to move immediately after it activates, which interrupts the rest of the animation so you can move to the next lever quicker. Simply do that, repeat on 2nd thing, then throw something at the last one. Some "throwing" levers require line of sight, that one doesn't, you only need to target and jump/move back slightly to hit it after doing the others.

You can jump around bridges without pulling the levers to drop the barriers. First one is harder, requiring a longer jump, second one is easy. Can always play it safe and have second person pull lever to drop the first barrier, then jump around the second.

Air jets? You don't even need summons, each person can pull two levers if done quick enough and the jet will still trigger. Then you need someone with enough run speed to go all the way back up and catch the last air jet (there's more than one, which gives you time to go all the way back up.

Else than that, nothing really troublesome, just need stats and something to unlock doors.

So basically you use exploits / bugs in the game, and not knowing every possible exploit means someone must suck.