Why does my FPS drop in Naraka group battles?

FPS dropped from 60 to 45 in group fights, causing serious lag. I increased page file size, but it made things worse, dropping to 55 FPS. I used GamePP BIOS Load Line Voltage Adjustment Wizard to set timing to 15-15-15-38 and voltage to 1.25V. MemTest86 showed zero errors after 6 loops. Temps stayed at 46-52℃. This verify step ensured my RAM was rock solid.