>Assume most of us are usually prepared for all situation when >we are on tour with a bag of at least one body and multiple >lenses, do we really need a heavy mid zoom, if I already >decide to bring a tele, like 70-200' and a wide, like 16-35 or >14 -24' and a standard prime for low light, like 50/1.4. Do I >really need a heavy mid range zooms, like 17-55 or 24-70?
Actually, I think your question makes the answer fairly obvious. The fact that you cannot envision a particular need for a heavy mid-range zoom and, therefore, question whether you should carry it indicates to me that you don't "need" it on the particular trip you are considering. That isn't to say that on some future trip you may see your needs differently and change the lens selection to include the mid-range zoom.
Only you can determine what photographic goals you have for any outing and you should select your gear to best support your goals.