Sounds like the gpu just doesn't have the power to do the rendering at full speed at 1080p in the most complex scenes (ie during the 'special attacks'). Likely a lower resolution is the only solution (assuming you don't have other gpu load increasing options like msaa or anisotropic filtering enabled).
Also, remember even if you have the maxwell 860m instead of the kepler 860m (I hate rebrands), it may be the same chip as the 750ti, but in a laptop it'll likely be extremely temperature and power constrained. This can cause lower performance than the desktop variant, even if it's running exactly the same chip - especially over longer periods of load (as if the cooling can't keep up it'll throttle when it gets heat soaked).
Also, remember even if you have the maxwell 860m instead of the kepler 860m (I hate rebrands), it may be the same chip as the 750ti, but in a laptop it'll likely be extremely temperature and power constrained. This can cause lower performance than the desktop variant, even if it's running exactly the same chip - especially over longer periods of load (as if the cooling can't keep up it'll throttle when it gets heat soaked).