What I ended up doing there, and it feels utterly cheap, but it wasn't out of me wanting to be cheap was:
1. From the place where the sniper rifle is, take down the guys with carbines (most are the rocket wielding brutes). With the available ammo, aim, and some luck, your mob count should be reduced a good 8-9 or so. Make sure to take out the bastard brute, far back, on the sniper platform with a carbine rifle.
2. Hug the right side, which isn't covered with brutes. Use the broken tunnels and you should be able to clear the area with no problem. Now, here's the disappointing part for me. After I did that, I got a checkpoint, some guys with choppers showed up, and the remaining brutes from the previous area simply disappeared. I was SO disappointed. It felt like the battle was stolen from me. My plan was to grab the carbine rifle from the guy on the sniper platform, and take out the remaining brutes. I also didn't know about the battle rifle rack back then. Curses!
I WILL return to that area again in Legendary once I finish my first legendary run. BTW, I've cleared levels 4, 5, and 6 after that, and strangely enough, they feel easy. Almost easier than heroic. Go figure.
*shakes fist at Bungie*
My solution was even cheaper, after I'd died a few dozen times in the area with the sniper rifle and turret, I took out a few of the sniping grunts, legged down the left of the map, as the wraith round the corner spawned I boarded it immeadiatly, pummelled the inhabitants to death, took it over, and went back to seek my revenge on the 7 or 8 brutes that remained.
Having the wraith made the next part a hell of a lot easier too.