Had similar problems.
Observation:
I had AHvoice open, horrible stutters and frame rates dropped to 2 at times. All planes were pulsing (fly fine 2 sec, warp, fly fine 2 sec, warp, fly fine 2 sec, warp, fly fine 2 sec, warp ...) very consistently.
Turning off AHv, relogging or restaring AH did not make condition go away, however rebooting did.
F.