Well guys - seems I have some of you confused. Let me begin by explaining the first key premise of flying any aeroplane of any type:

ATTITUDE + POWER = PERFORMANCE

This means that for any given attitude (pitch angle) plus power setting you will obtain performance or outcome. This is why jets are very much a by the numbers excercise, you learn the pitch angle plus the power settings required to obtain various speeds/ROC's etc. I have a power/attitude/speed table for all the aircraft I fly as a point of reference and it is the first thing I experiment with when I get a new sim model by going through take offs level flight at various altitudes, turns and descents before I go any further to get some idea of what power and pitch attitudes are required for level flight, climbs, level turns, climbing turns, descending turns and descent and approaches, to work out what is what with each aircraft if the information is not otherwise available.

You will notice with the 707 or 727 for example the initial takeoff pitch attitude is quite high and then is decreased in increments to about say 8 degrees or less in the climb. Your ROC will vary with temperature, weight and power. You will have noticed with the 727 that the flight deck angle or pitch on final at Vat is quite high and even in level flight the aircraft is flying at a particularly higher attitude or pitch angle that a lot of say non turbine aeroplanes. In descent the actual pitch attitude is quite flat without power and it is the apparent angle from the deck that gives a different impression, so generally say like for the 727 on descent using attitude and idle power the attitude indicator is only -2 or so degrees (dependent on weight and temps)

Level flight will have a certain pitch attitude, dependent on wing design, altitude and weight and power.

What we are trying to do here is descend managing the intertia of the aeroplane plus speed, so to obtain a certain performance what do you need to vary? Attitude or power, so it follows that if you are at flight idle (or basically zero thrust), then to obtain a certain performance you need to vary the attitude or pitch angle. Better to change the attitude than to be flogging the engines up and down and burning heaps of fuel in the process, why use fuel when gravity is doing the work for you?

The 3 degree ROD process I have described so far is to allow you to use the inertia and gravity momentum of the aircraft to descend with minimum power. Naturally if the ROD increases beyond reasonable limits you will need to apply or decrease power and change the attitude, so we are using power to control speed and attitude to control ROD and we keep this process going all the way down to touchdown. At the start of descent you lower the nose first, then allow the aircraft to start descending, then bring the power back. There will be level off points where you need to let the aircraft effectively fly level for a minute or two to reduce speed, the more drag the quicker the deacceleration, 707 and 727's are quite slippery or not as draggy so will take longer to slow down, during this slow down point you may need to apply power to maintain the performance you require. You will have no doubt experienced this or recall these phases as passengers in jet transport aircraft. The key to making this all work is anticipation and being ahead of the aeroplane by knowing where your going and at what points you need to slow down and or configure the aircraft. Those points are distance and altitude.

If you try the half the IAS method to manage your ROD you will find that you do have to apply and reduce power now and then but the changes will be minimal and by the time your below 10,000 ft you will generally be using say about 60-70% N1 and as you increase drag by extending flaps and then gear then you will need more power to maintain airspeed and then only have to make minor changes in pitch attitude to control the rate of descent.

Don't worry to much about the changes in speed of IAS v TAS v GS with altitude on the way down, the ASI is correcting this automatically and you have MACH indicator as another reference,  the altitmeter distance check will smooth this out for you and help you increase or decrease the ROD required to cater for changes in winds. You can go as fast as you like as long as you don't exceed the barber pole limits for the aircraft, generally aim to keep speed just below or add barber pole indications until below about F150.