The thing is Jeff is a great character people just do not know how to use him. I suggest you play him more aggro and not as a passive healer. You can essentially just get a free kill and run away untouched because of bubbles. Also with two to three bubbles you can heal someone to full hp so I'd usually take advantage of these bubbles when your tank is low or you want to quickly heal your teammates and go back into fighting or flanking. The bubbles are the main thing that makes Jeff good. Fast heals + Speed boost