EDIT: I was pointed out that Zen’s shield regen adds to passive healing. This post becomes redundant. Please move on. Thank you.
New Support passive (heal over time) is a huge debuff for Zen. In OW1, Zen was one of the few supports that could heal himself over time (due to his HP being mostly composed of shield). However in OW2, even Moira self-heals (without the need for her orb). So, unless you are a Zen God, why ever choose him?