I've done Hall of Reflections three times now, and the last time was the first one I didn't die on.
Part of this is the benefit of experience. You can read about an instance all you want online, but until you actually do it, you won't internalize the details.
The first time HoR came up in my early morning runs, I was completely unprepared -hell, I didn't know I had the gear capable of it until the picture popped up- and I dropped almost as soon as possible. It wasn't the proudest moment in my WoW career, bugging out of an encounter due to dread, but I knew I wasn't ready. I spent the next lunch hour reading up on HoR online, and when it came up in the queue again, I told myself I'm going to try.
"Oh crap," said one DPS. "@#$%!" said another.
The healer was unimpressed. "It's not a big deal," said the Priest. "You'll live through it."
Of course he could say that; he had a 5900 GS filled to the brim with ICC gear.
The first trash mob, I wipe. Everyone else is busy staying alive, so I figure that the trip is a short one so I release and fly back to the instance. When I get there, I realize I'd forgotten one of the things I'd read online: DON'T RELEASE AND RUN BACK! THE DOORS REMAIN CLOSED!
Luckily, after the first boss the doors flew open and I came back inside. The rest of the instance I didn't die, but it was a very near thing. I'm used to making an impact of some sort, but about half of the time I was healing myself to keep up with the load the priest was handling. I felt very out of place, kind of like the last time I tried my hand at healing an instance.
That brings me to another part of surviving as a melee DPS: understand tanking.
Doesn't seem so hard, right? You let the tank acquire threat, wait a couple of seconds for the tank to get a good lock, and then go behind and start supporting the tank. If the tank directs you to a different target, you go to the different target. If you see something bad getting ready to happen -like the tank standing way too close to the cliff in Pit of Saron that a simple knockback would turn the tank into a skydiver- you call out to let the tank know.
Well, the second HoR run gave me a different insight on tanking.
The first two times the PuG tries, we wipe on the trash. It was getting very frustrating, particularly so since I wasn't able to really get going before I watched in surprise as I pulled threat from something other than the tank's -and my- focus.
Time to reevaluate things.
The third trash attempt, I waited and watched. Those first ten seconds of the trash pull were the hardest ten of my pugging career, as I itched to close the gap and start taking the pressure off the tank. But as I watched, I saw something I hadn't before: the speed of the trash closing in on the tank was incredibly slow, completely unlike the trash in any other instance. The first one or two undead get there at the same time, but the last two or three are up to four or five seconds behind. It was those latter two that were giving me trouble. Therefore, I had to wait more than twice as long as I usually do before closing and starting combat.
Sure enough, that did the trick. I didn't die and I contributed significant DPS to the cause.
This last time I ran HoR -with Souldat as the tank- I put my knowledge to use and waited. Having run with him since the beginning, I knew Soul could handle the hits for a while. That wasn't a hell of a lot of comfort, as I sat and waited like a bump on a log for that last straggler to zero in on him. However, I knew my job was to a) keep myself upright so I could b) lay the smackdown on these undead. You can't do part B if you're a smudge on the floor, and if you've got a warrior tank instead of a DK or Pally, you need to give him/her that extra time to lock down the trash or the instance will turn into a threat-fest.
Each pull is different, and you can't assume that what works one time will work in another. When in doubt, err on the side of caution.