Personally I have not had that problem wit the HTC One, even after the Kit Kat update.
I do, however, know the the ability to be talking on the phone and using data at the same time will be going away with newer models of all Android phones. From what I have read, it is due to the movement away from the current dual path radios in the chips currently used in the various Android phones. The newer Android phones, like the HTC M8 are supposed to be better signal recently receivers (better at pulling in data signal and voice signal), but are have single path chips, that only allow data or voice, but not both at the same time.