Nick, while I have nothing to convince You about 17 cars I'm pretty sure that the peak torque of new WRC cars is a lot bellow 5000 rpm (Your graph), I guess 3500-4000 rpm could be right and the torque is definitely reasonably higher than from R5 car (Fabia has even higher torque than Fiesta). The R5 engines are half-stock units while WRC engines are purpose-built units designed from scratch.
Also I don't believe that the cars have only 380 Hp. This number apeared when somebody said that the new engines would have 80 Hp more but the key is that 2016 cars never ever had 300 Hp but much more. Again nothing in my hand but I do believe that the true power of 16 cars was something around 340 Hp (2.0 WRC were even stronger, even vintage cars like Octavia or Corolla WRC had real 320-330 Hp). New cars have 19% larger restrictor which might indicate something around 400 Hp.