50/50 Healing dps doesn't work in this game, it simply does not. Back in Vanilla nobody took feral or balance druids or elemental shaman or ret paladins.
Do you know why? Because their dps sucked and anything they offered as a hybrid could be done better than a healer.
I know you're probably thinking oh but we're a far cry away from Vanilla, it's an entirely different from then but here is the underlying main point;
If people wanted to take a dps or a healer, they would take a dps or a healer. Not something in between that puts out abyssmal numbers trying to do both roles badly.
It's very simple, jack of all trades doesn't apply in wow because that "jack" actually is not as strong as a jack, it's more of a 3 or 4 of clubs, while everyone else is an ace because they're specced for that role.