Just did this.
Had to do it with a pistol as it was the only long range weapon I had that was lethal enough (had a shotgun and heavy rifle, which is terrible for aiming anywhere past 10 metres).
Was really tough but once I got the lay of the land wasn't too bad. I used the auto-save which is basically from when the cutscene ends and play begins. Changed to a gas grenade and pistol, threw the grenade as far towards the back as possible where the 2 mini-gun guys are. Then just went pistoling everyone else around the level as well as throwing a couple of concussion grenades in that little area to the right where the snipers are all poised.
Keys are to make sure you use the barrels and grenades imo. Obviously you need to switch to the EMP as soon as the big dog turret gets dropped as well.
Also make sure you have plenty of stimpacks and painkillers. I managed to do it with 1 painkiller and 3 stimpacks, so if you have more again you should be fine.
It's do-able.
Cheers, thanks for the tips. One thing I wasn't doing was using the EMP, so now it will be the first thing I try.