I'm not familiar with your Sennheiser set, but I think you want to set the DVX input to mic level, not line level. All the portable wireless sets I've worked with put out mic level signals.
THE LECTROSONICS AND ZAXCOMS ARE PULLING OUT LINE LEVEL - THATS THE WAY I HOOK IT - LESS PROBLEMS WITH HAM FROM THE GROUND LOOPS
for the small zen that pull mike level only ( or very modest line)
place the dvx on mike -50 db , close the phantom , adjast your transmitter level the way you dont distort and dont have to week saignal , adjust the camera on the half way( 12 o clock) , then adjust the output level the way your picks when the person speaking normally would heat at least -12 ,10 dbfs