I tried some of the GC leves for LL just now which are pretty nice for solo xp. Main problem is the npc mentions you can get considerably more marks based on performance, which I'm not seeing.

For one leve you have to kill 3 types of mobs and the minimum requirement is 2 of each or 6 total. I managed to kill 5 of each or 15 total within the allotted time and still received no additional bonus. Anyone know if I'm not doing enough or if it is bugged? I am rank 38 doing the R30 quests at 3 star so the enemy level is 36.