Scored 64k with a 2.21x time bonus (34 mins) on Legendary, so this should be feasible for most people on heroic, or on normal with a skull or two.
Things to note:
The main deciding factor for time for most people will be the beginning ship part, I crashed twice during this part. The turrets are worth a decent amount of points, so kill any that you can.
Once you're inside, use your SAW on the first knights and it will take them out pretty fast.
You should get a Promethean Rocket Launcher (Incineration Cannon) fairly early on. If you save the ammo for knights, you should have enough ammo to kill about every knight in the level as long as you pick it up as you go. The only time I had to switch to something else was on the 2nd or 3rd platform around the Didact, but I found more ammo soon after.
The time still counts down during the final 'interactive cutscene', and will take about a minute assuming you don't fail it.