Captain is technically 2 uruks for 4 twilight (with sentinel), which is great imo. Also recurs shagrat. Not sure about Regular, but those two minions were the core of my favorite movie block uruk deck, and honestly, this list is not all that different, it should have decent swarming potential on site 6 even from a few twilight. Maybe can remove a Regular for a 2nd troll, but I'd actually have to play movie to test it, but even after like 2 years of not playing the format, I'm still bored with all the freeps sides I'd be willing to run lol.
Maybe:
-1 captain
-1 regular
-1 grond
+1 troll
+2 marauder