Why does FPS drop to 30 during ultimate abilities in Dark Reign?

During combat climaxes, particle effects explode but the frame rate drops like a cliff, which is incredibly anxiety-inducing. I tried disabling all shadow effects in-game; FPS rose by only 5 frames while the graphics became hideous. I then used GamePP Power Plan Switcher to lock High Performance and bound the process to 8 P-cores. RTSS showed frame times improving from 25-40ms to 11-14ms. Finally, AIDA64 confirmed my fan speeds stabilized at 1800-2100RPM.