Act 4: C1 - Priorities

Just follow the path to a cutscene. Follow the little crybaby to a lift and press the button, then make your way to the opposite lift to go down. Turn the valve until the gates are all down, then quickly get into the waterway and take cover about two trenches up. To the left they will try to turn their valve to flood your position, but you just need to keep the guys away from that side. Go up a trench and toss a frag or two, then finish off the rest and get over there. Should swap the bow for the longshot, then take the next lift down.

Get the longshot for the bow and grab the ammo. Outside there are wretches to the left and a mauler to the right. Hit the mauler, but look to where Dom goes. Get to the opposite of Dom, which is most likely to the right side, so that someone will be able to hit the mauler. Take out the wretches or the big guy first, don't try to do all first. Some ammo if you want it and you can use the boomshield for the next fight.

Across the small bridge will be a pretty difficult fight. If you brought the shield, I say plant it between the cover and then just stay here as you toss frags to the troika. Then you'll need to take out the drones on the ground before aiming at the snipers on the sides. It's hard if you try to move around holding the boomshield, trust me.

After, ammo to the back right and the guns dropped, then go to the left side where you see a yellow terminal. DO NOT use the one in the middle, go to the one by the wall that has the magnifying glass when you're close, that one has a collectible. Then use the one in the middle.