Why does my World of Warcraft frame rate drop during raids?

In a large raid, my FPS plummeted from 60 to 45. Setting fans to 100% manually caused thermal spikes and worse performance. Using GamePP Fan Curve Panel, I set 80% speed at 75℃ and optimized threads. 3DMark stress tests showed temperature stabilizing at 72-75℃ and frame rate converging to 58-62 FPS.