In the EC130 and as well in the new production AS350B3's, there is a potentiometer which monitors yaw movements which will increase the RRPM (thru the fadec) when T/R limits are being reached (when the 10% control margin is getting close). It is increased to something like 402 from 394 for the purpose of providing more T/R authority at those critical times, such as lifting heavy loads in the hover at altitude. Density altitude is also factored into the equation.
To me this supports Nick's comments that overpitching at altitude likely could lead to reaching or exceeding the 10% control margin for the 350's and thus insifficient T/R thrust.