This could be stating the obvious: but pheasants, as you are finding out are real wary creatures. It's very important when you get out of the vehicle to keep the noise at a minimum,don't slam doors,don't run beeper collars,don't keep blowing on your whistle, shouting back and forth, etc.

Noise will do more than anything to keep those birds 100yds. in front of you than about anything else. Also, have you tried blocking? We somtimes hunt a field from both ends towards the middle pinching them between us.

Another spooky bird tatic is splitting up and working one man - one dog. Work slow; it sounds as if your dogs are good enough to work with you. We take 3-4 guys and start out as far away from each other as we can get, then we all workto the same corner.....we try to heard the birds the best we can.