Thanks rif_raf. You put out a lot of interesting info there, but.... I disagree with your statement:
If that gauge is an engine torquemeter reading, then all of that torque is being transmitted through at least part of the MRGB before being split between the tail and main rotor drives.
In the gearbox section on the above RR 250 engine, you will note that the power output to the left goes to the main transmission. I added the arrow to the right to show that the same gear drives the tail rotor and both outputs affect the torquemeter reading, but only the power output shaft to the left goes through the main transmission. In other words, the tail rotor does not go through the main transmisssion (MRGB).
I'm sure that you are correct on many helicopters, especially most if not all multi-engine models, but the Bell 206/407 series powertrain using the above series engine would not apply. Thanks for the solid information.