So, I have come to a similar conclusion Slacker George came to, in regards to the water/pillar room in the fortress on crushing. Here is his post (http://www.avsforum.com/avs-vb/showthread.php?p=12275709#post12275709) about the following exploit.
Normally the enemies won't spawn in unless you drop down into the water. But if you backtrack back to the courtyard area and then return they'll be there waiting for you. Now just stay up on the platform and pick them off one by one at your leisure. A couple of pirates will spawn in right next to you eventually, but they'll just ignore you until they drop into the water.I have only been able to do this room with the aforementioned exploit. I finished the rest of the game on crushing in a breeze, albeit there were a few sticky situations. I think the room can be accomplished with the right weapon selection prior to entering the room, and of course with quick shot skills and timed cover locations. Has anyone successfully completed this room on Crushing? If so can you please reply as to how you did it in sort of a walk through method, as its the only room that has me beat. If you could please use the spoiler tags as others may not want to read this. Thanks in advance. What an awesome game, even the wife is playing it (on easy to start).

Well, if anyone is in this thread they should know it is 100% full of spoilers from the title alone.

I dropped down in the water and just attacked in sections, using MANUAL cover instead of auto cover. When I cleared an area, I moved to a different area opposite of where more enemies were dropping on me.

For me, manual cover is key. This is where you hide behind something by walking to it without touching the auto-cover/roll button. This allows you to avoid damage, but it is much easier to control the line of sight to shoot someone without exposing yourself. Remember to use R3 (a thumbstick press) to switch shoulders as it is needed with this method.

Once you nail this method down, you clear a "wave" of enemies and move to another location. From the moment I drop down, I try to kill all but one of the first wave, being sure to hit the balcony enemies too. I then go directly forward on the other side and turn around to clear the bad guys who come next, and I think that's it. I use the manual cover method and good aim to maintain control of those coming at me. Different weapons work... the grenade gun is good for enemies in hiding or in a far distance, but the pistol/semi auto guns take care of everyone else just fine.

I was similiar to Joe, I use manual cover most of the time. I will say it took me a crap load of times to complete it that way. First time I did it was indeed by finding the exploit from going back looking for ammo.

Thanks guys...I'm real good at the manual cover, shoulder switch. I just can't get past the first 2 or 3 guys. If I hit the guy on the ground as he is approaching me, I can usually hit one of the balcony guys. But killing 2 generates the next wave to start. The problem is then the move to the other wall. I get nailed by one or two of the shots from the remaining balcony guy and then I'm toast by one of the guys in the water who are in swarm attack mode (or vice versa). There just aren't enough cover options to allow health regeneration. Ie...if you take a shot your pretty much toast. Joe...you make it sound so easy. Are you sure you did it on crushing.;) Did you go in with any particular pistol. I'm thinking the fully loaded revolver is a much better choice.

Heh, I often try to beat all my games on the toughest difficulty. I did it with Heavenly Sword, God of War, etc. I'm sure I did Crushing on Uncharted. I think it was tougher for me the first time I played (I skipped Normal and played Hard first time through) because I was still learning the controls and the attack system. It takes a few tries, but it is do-able.

Take out the balcony guys early after the first few kills. You can use auto cover for early enemies if that helps your rhythm (crouch near that fallen bench as soon as you fall). The enemies stay behind cover themselves at first, so clear out the nearest ones, focus on the balcony guys, then use manual cover and practice to clear the rest (two waves come at first if I remember correctly... first to your left). For the last group, I go to the other side (forward, not left) so I can turn around and kill the new enemies that swarm.

Heh, I often try to beat all my games on the toughest difficulty. I did it with Heavenly Sword, God of War, etc. I'm sure I did Crushing on Uncharted. I think it was tougher for me the first time I played (I skipped Normal and played Hard first time through) because I was still learning the controls and the attack system. It takes a few tries, but it is do-able. I was just kidding joe.:) I played it the way you did too (Hard first, then Crushing), I didn't think Hard was all that bad, as long as you figured out the cover system. Crushing wasn't even that bad either, once you got past the fortress. Like I said, you make it just sound so, so easy. When I went through I was very close to hurling the controller on the floor. I will try out your tips at a later date...I'm officially Draked out for now. When I do go in, I'm going to try to take the Wesson, and hopefully the shotgun if I can do it.

I do love reading other forums that when people asked for help with this room their reply was "if you think this was hard, wait till you get to the chapter Trapped." It's funny that no other fight in the game is as hard as this room. I personally thought Trapped was a really fun room, once I found the proper way to enter the room.;) I also found out that if you found the spot and pattern to beat the level on Hard, it was much the same on Crushing. If you just don't get shot, the game goes by fast.

Just thought I would let others that attempt this room, it can be done and quite efficiently if you come in with the fully loaded Wesson and a shotgun minus a blast or 2 (used to take out the guy in the side of the tunnel leading to the water room). Within 5 or 6 attempts I had it nailed. Good luck to others that attempt the Crushing difficulty.

Well, I kinda approached this room differently. And Dogdoctor, I actually thought of your strategy in the RFoM cathedral for this one! I needed a cover spot where the bad guys would funnel in toward me, and where I could pick them off in a more orderly fashion.

Start by jumping off the ledge and run toward the one guy on the ground. Take him out, pick up his bullets and head to the very back, to the right of the high structure where another bad guy is standing. Hug the wall...the guy up top won't be able to get you. Next, take a few quick shots at the guy on the high platform in the middle. If you don't get him here, don't worry....you'll get another chance.

Back off, back along the side of this wall, and get ready for the guys to basically just walk into your sights. Take them out. After the last guy, run over to the other side of this platform....hugging the wall again. Take another few shots at the middle platform guy again....taking him out this time. Next, get ready for the second wave of bad guys coming from the opposite side.....they'll walk right into your sights again. Try and pick up a shot gun if you can. Use it to take care of the bigger shot-gun guys.

One last guy....the guy up high at the back. Slowly ease your way toward the middle of the room...and when you see him, take him out with one shot gun blast.

Took me two attempts.