This definitely happens.
I run a fairly OTT rig, where I can play Arkham Knight with a consistent 60fps under heavy graphical load without strain on my resources, yet in max level warzones, I suffer from stuttering and am benching 25-30fps, and in lowbie warzones I can easily get 100+ fps in the same combat circumstances (heavy player and aoe presence).
I've looked into this and cannot seem to find a solid answer on this issue, and it infuriates me