Maybe you are not explaining your point clearly enough? Clearly Agusta will run out of power like any machine. The Hover OGE graph tells you when that will be. It just doesnt tell you whether the limiting factor will be Tq N1 or TOT. Does that matter? Most more modern aircraft provide you with a "PI" or first limit indicator which tells you when you get to the limit on any of the parameters. It doesnt make much difference to me which one it is.