This mission is actually very simple to get par score on. It takes a few skulls and no rushing for par time. I played this level on Heroic with the following skulls and achieved a respectable score of 30k.
Catch - Enemies throw more grenades. Alot of grenades will be thrown so watch out.
Famine - Weapons dropped have half ammo. After the first room against the brutes, there is alot of ammo crates, ranging from Carbines, Beam Rifles, and Swords.
Fog - Disables Radar
Jacked - Can only enter ground vehicles by boarding. No vehicles on this level
That's Just... Wrong - Enemies become more aware.
Personally I found this level easy carrying a Beam Rifle to lower the shields of elites and to kill jackal snipers from a distance. The other weapon I carried was a Carbine, ammo is plentiful after the first area and can be used to dispatch every enemy. Try to only use plasma grenades on unaware enemies, or from a distance, as they will rush toward you when you stick them.
Since the whole mission is pretty straight forward with these weapons I will be describing how to get through the first room you spawn in.
You will start off on a platform with two brutes shooting you, while backing up away from them you will want to take one out with the needler you spawn with, which will make the other one go berserk. Pick up the dead brute's plasma rifle and take out the grunts while avoiding the brute. By this point you should have a few plasma grenades, which you can use to stick the final brute.
The next few waves are 2 brutes and 4-6 grunts, you basically want to do the same thing as before, but this time you will want to take cover behind the huge columns at one end of the room. You will eventually kill brutes with carbines and will want to replace your brute plasma rifle with the carbine. Now you can take out the grunts with ease and depending on your ammo can quickly take out the brutes as well.
From here on out its a cake walk (as much as it can be). Focus on killing every enemy that you come across, try not to backtrack that much, and take your time and stay back. Also, when you see enemies fighting eachother, try your best to take out the guys as they become one shot, especially the elites as they offer a good amount of points. As long as you have 26k or so by the time you hit 50 minutes your good to go. Try to limit deaths, dont restart from checkpoint since it deducts points, and only backtrack if you need ammo, if you miss an enemy or two you will be fine. I finished the level in 42 minutes (1x Multiplier) and had 28k going into the final room. Good luck!